Kamala Harris’s campaign thought it knew exactly how to beat Donald Trump. With just weeks left before Election Day, it warned over and over that he was “unhinged, unstable, and unchecked.” But instead of amplifying that message, Future Forward—the $900 million super PAC that the campaign was counting on for a flood of ads—had a different plan. The campaign leader Jen O’Malley Dillon grumbled in private meetings that the group had gone rogue, threatening Harris’s chances of winning. O’Malley Dillon told her team that she had never seen anything else like this.

Usually super PACs follow the lead of the candidates they support, while taking on less savory tasks, such as viciously attacking their opponents. But Future Forward had built a bigger internal research program than the campaign had, and its leaders saw only one clear path to victory. Harris had to stay laser-focused on the economy. She had to present herself as a disrupter, not as a protector of the status quo.

The Harris team liked Future Forward’s economic ads, but they believed that Trump’s approval ratings were dangerously high. There needed to be a sustained, direct attack on him. They also argued that the super PAC had delayed its advertising for too long, had not targeted those ads enough to different groups of voters, and had failed to properly distribute money for get-out-the-vote efforts. So Harris’s team shifted strategy to do some of that themselves. Harris told reporters that she saw Trump as a fascist, and recruited some of his former advisers as her spokespeople.

Future Forward’s team scoffed. “People might not mind ‘unhinged’ if their fingers are caught in the door,” one Future Forward strategist started telling colleagues inside the organization. They did not believe that there was evidence in the voter data to justify a switch back to the politics of protecting democratic norms.

Listen: A former Republican strategist on why Harris lost

Campaigns and groups such as super PACs are not allowed to directly coordinate on many ad-spending decisions, but there are legal ways for them to signal their desires. Future Forward began quietly raising alarms in private polling memos that it knew the campaign would read. O’Malley Dillon publicly suggested in September that top donors give to other groups in addition to Future Forward.

“They are very driven by ad testing, which is spot by spot—a lot of trees. But the way I see it, the presidential campaign is a forest,” a top Harris-campaign adviser told us about their objections to Future Forward’s approach. “The candidate is the candidate, for good or bad. You have to follow their lead.”

Neither side would change course. When Harris eventually lost, she did so with the backing of two different efforts that sometimes worked at cross-purposes, an error that both sides still believe may have cost Democrats the election. “We should have been one streamlined engine whose true mission was to elect Kamala Harris and defeat Donald Trump,” Rufus Gifford, a veteran Democratic fundraiser who worked for the Harris campaign, told us. “And it is clear that that was not always what happened.”

Once the election was decided, the remaining restrictions on communication and coordination were lifted. But seven months after the loss to Trump, there has been little meaningful discussion of what happened between the fighting factions of the Democratic Party—although O’Malley Dillon and Chauncey McLean, a co-founder of Future Forward, did meet on Wednesday to talk through their post-election views.

Anger has continued to fester as Future Forward positions itself to play a major role in the 2028 presidential election. One strategist involved in the controversy has taken to calling it “the largest fight for the soul of the Democratic Party that no one is talking about.”

The unusual circumstances of the 2024 presidential election—a brash, prototypical, seemingly Teflon candidate on the Republican side, and a last-minute candidate switch on the Democratic one—set the stage for the collapse of the traditional super PAC–campaign dynamic. But the resulting conflict also revealed a fundamental flaw in the multibillion-dollar architecture that Democrats had built to defeat Trump, raising questions about who controlled the Democratic Party in 2024, and who will steer it into the future.

“Is Future Forward meant to be the group that determines the strategy for the presidential candidate? I’m not sure,” one major donor to the group told us.

This story is based on interviews with more than 20 senior Democratic strategists, donors, or advisers who worked to defeat Trump last year, as well as a review of a trove of previously unreleased Future Forward testing and briefing documents obtained by The Atlantic. Many of the people we spoke with requested anonymity because they typically avoid public comment, were not authorized to speak, or are strategists who want to work for future campaigns.

Defenders of Future Forward say the party needs to continue to replace its reliance on all-star campaign gurus and activist groups with cutting-edge data science that can precisely measure what voters want. They believe that Harris’s campaign ultimately betrayed her candidacy by drifting away from the central economic narrative of the race—a choice between a Democrat who would make things better for working people and a Republican who would reward his rich friends. "It’s pretty clear that there was one path for her, and we saw success there—we had to make it about what voters wanted, not what we thought they should care about,” one person involved in the Future Forward effort told us. “We will never know if it would have been enough, but it is the question going forward.”

Read: Twilight of the super PAC

Three weeks after the election, Future Forward leaders sent a private memo to their donors. They claimed that Future Forward’s television ads had been about twice as successful at persuading people to support Harris as “other Dem” television spending, a category dominated by the Harris campaign. “Our execution,” they concluded, “proved more effective at moving the needle.”

The next step, they told donors, was to expand Future Forward’s preparations for the 2028 campaign. They plan to provide “testing for the individual would-be candidates so they can learn—early—what works and does not work for them and with the general electorate,” the memo said.

“There is an opportunity,” they told donors, “to fundamentally improve how Presidential campaigns work.”

Veterans of the Harris campaign and members of other outside groups, however, have argued against an expansion of Future Forward’s role and pushed for a rethinking of how super PACs are used. “I think our side was completely mismatched when it came to the ecosystem of Trump and his super PACs and ours,” O’Malley Dillon said on Pod Save America, the same day that Future Forward sent its memo. Harris senior adviser David Plouffe, appearing alongside O’Malley Dillon, was even more blunt about the GOP advantage: “I’m just sick and tired of it,” he declared.

“One group making the decisions for the entire ecosystem and thinking they were making better decisions than the campaign and the candidate should not be how we move forward,” another senior Harris-campaign adviser told us. “They don’t have the experience. They don’t have the understanding of the nuance of this. They didn’t know better.”

America’s first political campaigns were self-financed by wealthy candidates like George Washington, who used their money to buy voter support with booze. In the second half of the 20th century, Congress decided to limit the amount of money any single person or company other than the candidate could use to influence American elections and to outlaw vote purchases. Federal courts pushed back in 2010, over the objection of Democratic Party leaders. Some of the laws meant to limit corruption, they decided, violated the First Amendment rights of the rich.

Whiskey can no longer be traded for votes, although donors can throw alcohol-soaked parties to celebrate the general notion of voting. The wealthiest Americans, companies, and unions get to spend unlimited amounts to influence elections’ outcomes, but those funds cannot go directly to the candidates’ campaigns or to their political parties, which have strict contribution limits. The really big checks go to “independent” nonprofits, which often do not report their donors, or to so-called super PACs, which disclose their activity to the Federal Election Commission. Future Forward raised money both ways.

Under the new system, major-party presidential candidates need at least one outside operation with deep pockets in their corner, or else they place themselves at an enormous disadvantage. Candidates are barred from privately “coordinating” on some types of spending with these groups, but they can communicate in other ways: Their campaigns can signal their strategic desires by talking to reporters, who print their words, or by way of discreet posts on public websites. Super PACs can do the same or speak directly to the campaigns through “one-way” conversations, often Zoom briefings where the campaign team does not speak or turn on their cameras.

Candidates also have the ability to signal donors to support the “independent” groups of their choosing before the start of a campaign. This typically involves placing trusted aides at the outside groups, as Trump did at the start of the 2024 campaign cycle with a group called MAGA Inc., or as Barack Obama and Hillary Clinton did with Priorities USA. Joe Biden decided to go a different direction in July 2023, when his advisers Anita Dunn and O’Malley Dillon gave interviews to The New York Times that strongly implied that Future Forward had received Biden’s unofficial super-PAC “blessing.” A top Biden fundraiser, Katie Petrelius, joined the group to encourage donors.

McLean and his team quickly incorporated the Times article into the March 2024 pitch deck they showed donors, a copy of which we obtained. But unlike MAGA Inc., Future Forward did not present itself as simply an extension of the Democratic campaign, with Biden himself, and later Harris, as its north star. Internal staff talking points—released just before Election Day and marked “not for distribution”—described the group’s power as coming from its impact on the electorate, not from “being anointed or pre-determined” by a candidate.

The group’s mission had instead been set at its founding, after the 2018 cycle, when strategists who had met during Obama’s 2012 reelection campaign concluded that they could bring a new level of mathematical precision to the art of voter influence and apply that wisdom to the spending of dozens of Democratic-aligned groups. During the 2024 campaign, the group granted more than $220 million to 73 organizations, including Emily’s List and Somos Votantes, for advertising, issue advocacy, voter mobilization, and registration. Future Forward has never issued a press release, and with the exception of two summer Zoom briefings, where questions were screened, the leadership has mostly avoided larger group conversations about strategy with the other outside operations fighting to defeat Trump.

Future Forward’s approach infuriated many members of veteran Democratic voter-mobilization and persuasion groups, who felt sidelined from both donors and from the strategy conversation. “Resources were not allocated early enough, or to long-standing organizations that know their audiences,” Danielle Butterfield, the executive director of Priorities USA, told us.

Read: The shadow over Kamala Harris’s campaign

But Future Forward believed there was a superior way to run campaigns and allocate money. By March 2024, it was telling donors that it could produce “the absolute best ads that are proven to be effective across platforms” with a voter response rate “55% better than the average ad.” Over the course of 2024, Future Forward conducted hundreds of focus groups and collected more data on American voters than any other political effort in history, including more than 14 million voter surveys in the final 10 months before Election Day. The group created and tested more than 1,000 advertisements to support Harris’s presidential bid from dozens of ad firms, using a randomized-controlled-trial method that compared the vote preference of people who had seen an ad against those who had not. The best-testing spots blanketed the airwaves in swing states starting in August and were used to purchase more than 3 billion digital-video ad impressions.

As a matter of fundraising, the pitch was a massive success, attracting more than 69 percent of all Democratic presidential super-PAC dollars—more than three times the share of the top super PAC in 2020, according to an analysis by the independent journalist Kyle Tharp. Much of that money came from America’s wealthiest Democratic supporters, such as Microsoft co-founder Bill Gates, former New York City Mayor Michael Bloomberg, and Facebook co-founder Dustin Moskovitz. (Laurene Powell Jobs, the founder of Emerson Collective, which is the majority owner of The Atlantic, gave to a part of the Future Forward effort that does not disclose its donors, according to The New York Times.) For context, $900 million is more money than the Democratic National Committee raised last cycle and nearly twice as much as Trump’s own campaign collected. The Biden and Harris operation ultimately raised $1.2 billion.

“Future Forward wasn’t started by allies of one candidate or campaign,” the group’s talking points declare. “While it can upset (or even upend) the status quo in politics, no decision is made that isn’t in the best interests of impacting the outcome of the election.”

The Biden and Harris campaigns operated with a different model. They had a similar data operation, with horse-race polling, focus groups, and randomized-controlled trials of ads, but it was overlaid with a crew of veteran campaign strategists. Biden and one of his top advisers, Mike Donilon, believed from the start of his campaign that big themes about individual freedom, democracy, and Trump’s character would shape the outcome. Their goal was to use the data from ad testing to inform the judgment of the senior advisers, not to determine what they would do. Future Forward had a different approach.

“I think they thought that if we were doing something different from what they were doing, we were stupid,” a third Harris-campaign strategist told us. “The reality is we just believed in the strength of our strategy and disagreed with theirs.”

Tensions between the two approaches surfaced early. Concerned about Biden’s relatively weak position in polling, the campaign launched an ad blitz in late 2023, aiming to reset voters’ views of the president. The campaign specifically targeted Latino and Asian audiences. Future Forward, which had long favored advertising close to Election Day, held back, even as MAGA Inc. began going on the air the next year. The first Future Forward super-PAC spot did not run until after Trump’s indictments, felony convictions, and assasination attempt; the Republican convention; and the switch to Harris. The election’s exit polls showed that 80 percent of voters had made up their minds before the end of August, when the full force of the group’s spending hit the airwaves.

From the start, there were doubts inside the operation about Biden’s view of the race. At the beginning of 2024, the group secretly commissioned 154 ads for Biden and tested them from February to April, according to another internal document. The results suggested that the single worst ad it tested echoed the threat-to-democracy themes that Biden’s team had embraced—casting Trump as breaking from presidential norms, seeking revenge on his opponents, and threatening to put them in jail.

Biden nevertheless launched ads in June that highlighted Trump’s recent felony conviction and questions about his sanity. “Something’s snapped,” Biden started saying of Trump. Future Forward insiders told us that they’d planned to start airing ads after the first debate, in June, hoping that the face-to-face meeting between Biden and Trump would mute concerns about the president’s age. When the opposite happened, the Biden team made it clear through various channels that they still wanted Future Forward to start spending to shore up Biden’s position. After all, they had blessed the group, and many of Biden’s top donors had made contributions.

Dunn, the closest of Biden’s advisers to Future Forward, informed the campaign that the group did not think ads defending Biden at that point were a good investment, according to people familiar with the conversation. McLean later described the decision to refuse Biden’s call for help as the hardest choice he had ever made. Biden, the group concluded, was the only one who could prove to voters that he was up for the job, even if donors were not withholding checks to try to force him out of the race. No outside group, no matter how well funded, could cause voters to unsee what they’d witnessed.

After Biden left the debate stage, nothing about the Democratic bid proceeded as planned. Despite the chaos, both sides of the $2 billion effort to defeat Trump found themselves working from the same playbook in early August, when Harris hit the campaign trail backed by a massive introductory advertising push by her campaign and Future Forward. Those early ads shared common traits—a tour through Harris’s biography, a focus on the economy, and a pitch that she was offering the country something different. “The data continues to point to the benefits of a mostly forward-looking and largely economic campaign,” Future Forward concluded in an August 9 messaging document.

"We built a coherent story: This is an economic contrast; she’s going to be better for your bottom line than he is,” a Future Forward strategist told us about the group’s ads. “We weren’t just taking the top-testing ads off the spreadsheet, because then you would have gotten gobbledygook.”

But the agreement broke down in September. Harris’s advisers knew that economic concerns ranked highest for voters, but they decided that those issues would not be enough to defeat Trump. Trump’s approval ratings increased after the July assassination attempt and the Republican convention, as the “something snapped” argument faded away. Harris’s campaign believed that no one had set a clear negative frame for Trump. Over hours of internal debates, it came up with a new, triple-negative tagline: “unhinged, unstable, and unchecked.” Expecting that Future Forward would not shift course, it bought advertising to fill what it saw as the gaps left by the super PAC.

Harris began to appear at events with Liz Cheney, the former Wyoming representative who was once Republican royalty, and new campaign ads featured former Trump advisers warning of his return to the White House. The campaign believed that it could improve margins among moderates and the college-educated conservatives who had long been concerned about Trump’s behavior. For Future Forward’s number crunchers, the message switch was a disaster.

The group sent up a warning flare. “Make the argument about voters’ lives,” declared an October 15 document posted on a website that campaign strategists could read. “Our task remains more about Harris than Trump.” By embracing Cheney and other conservatives, Harris was hewing to the unpopular status quo and defending institutional norms at a time when up-for-grabs voters wanted change. The document noted that ads focused “on Trump’s fitness as disqualification alone, without tying to voter impact” were among their worst-testing. The document included polling results that found that 53 percent of voters nationwide said they preferred a “shock to the system,” compared with 37 percent who favored “a return to basic stability.”

The differences in approach were so stark that, at one point, a data firm working with Future Forward worried that the campaign was using faulty data. In fact, both the campaign and the super PAC were using highly sophisticated methodologies for their testing, and the main issue was interpretation. “Future Forward’s theory of the case didn’t change when the case—when the race—changed quite a bit,” a Democratic strategist working with the campaign told us.

The Harris strategists were not the only ones concerned about Future Forward’s conclusions. Inside the super PAC, people focused on outreach to Latino and Asian American audiences were worried about the group’s decision to turn away from creating targeted ads, after Future Forward’s testing showed that those populations were best moved by the same ads as the rest of the country, according to people familiar with the discussions. For voters who did not speak English, the group ran ads in eight languages.

Read: Kamala Harris and the Black elite

At the core of these strategy disagreements was a debate over whether ad tests that focused on measuring vote-choice persuasion had limits. Some strategists argued that ads also had to build a sense of political and ethnic identity, and excite people to get more involved in politics or share messages on social media. Rather than just respond to public opinion, they wanted to try to drive it in new directions. Trump had proved himself a master of elevating relatively obscure issues—such as government-funded surgeries for transgender people—to change the entire political conversation.

“There is an art and a science to persuasion,” Jenifer Fernandez Ancona, a co-founder of the Democratic donor group Way to Win, told us. “It requires striking an emotional chord with people that will stick, and that goes beyond what can be captured in randomized control trials alone.”

Anat Shenker-Osorio, a Democratic data strategist who works with Way to Win and has criticized Future Forward’s methods, argues that ad testing in online panels creates an artificial environment where people are forced to watch the tested spots. “That does not mirror conditions in real life,” she told us. “This testing cannot tell us what would cause people to pay attention and what would cause your base to want to repeat the message. What would cause your base to wear the equivalent of the red hats?”

A Future Forward spokesperson told us that this critique was misguided. “Data can’t solve every problem, but it shows what voters really think, not what people who work in politics wish they thought,” the spokesperson said.

Others complained that Future Forward’s decision making on ads was too secretive. Ad firms got paid for production costs, and then submitted their spots to Future Forward for testing—and they received a commission of the spending, at a rate below industry standard, if their ad was chosen to run. About 25 firms got paid for ads that aired. But about 12 percent of the group’s ads were made byaffiliates of Blue Sky, a firm partly owned by McLean and Jon Fromowitz, two leaders of the group, who were making the decisions. Other ad makers received a larger share, and Future Forward said that it was not unusual for large campaigns to have strategists who work on ads.

“Who watches the watchmen?” one person familiar with the operation told us, explaining the risk of self-dealing.

Since the election, Future Forward has continued to churn out voter-survey data with the aim of shaping how Democrats communicate with voters. The regular “Doppler” emails, which are sent privately to a select group of Democratic officials and strategists, test everything from the social-media posts of lawmakers to podcast appearances by former Transportation Secretary Pete Buttigieg, and excerpts of rallies featuring Vermont Senator Bernie Sanders.

In these messages, party leaders are still urged to “make criticism of Trump economic and personal,” avoid personal attacks, use specific numbers such as “$880 billion in Medicaid cuts,” and create “vivid contrasts” such as “tax breaks for the wealthy vs. food aid cuts.”

The Democratic National Committee, which is working on an audit of the 2024 campaign due this summer, is expected to look at the campaign’s relationship with Future Forward, say people familiar with the plan. But there’s still no clarity on how the party and its top candidates, donors, strategists, and data wonks will choose to structure the 2028 effort to win back the White House.

Everyone we spoke with for this story agreed on one thing: What the Democrats did in 2024—using two competing camps that deployed conflicting strategies—cannot happen again.