Pierre Poilievre is counting on the budget balancing itself. Almost.

There are some mostly vague plans for spending cuts in the Conservative election platform Mr. Poilievre released Tuesday, but it’s not enough to pay for all the party’s promises.

So instead, the Conservative platform relies on the hope that their policies would cause a big economic boom, mostly in the oil and gas sector. They are counting on that boom raining tens of billions of dollars into Ottawa’s coffers.

This is happy thinking, even magical thinking, especially at a time when a trade war with the U.S. has clouded economic forecasts with fears of a recession.

Both the Conservatives and the Liberals promise their policies will lead to economic growth. But it’s the Conservatives, in a break from usual practice, who are already counting the cash.

And they are counting big: By the fourth year, according to the Conservatives, their hypothetical Canadian economic boom would bring in $24.7-billion more in annual revenues than current projections.

“They are basically forecasting that their economic policies will nearly double economic growth,” said economist Mike Moffatt of the Smart Prosperity Institute. “That’s exceptionally optimistic.”

Once upon a time, in 2014, Conservatives ridiculed then-Liberal leader Justin Trudeau for arguing that if the government committed to growing the economy, “the budget will balance itself.”

Mr. Poilievre is now embracing the same idea to reduce the deficit – although to be fair, he’s not actually committing to balancing the budget.

If you cut those hopeful “revenue gains” out, the Conservative platform would actually increase the annual budget deficit, starting next year, by roughly $10-billion a year.

That’s the only apples-to-apples way to compare the bottom line in each party’s platform, and by that measure, the amount of red ink in the Conservative platform is not a whole lot less than the Liberals’. Mr. Poilievre, who spent 2½ years attacking Liberal deficits, isn’t planning to slay them.

It’s pretty obvious why the Conservatives built their platform this way. It’s a political document, and the job at hand was balancing political objectives.

Mr. Poilievre wanted to promise big tax cuts and lower deficits, but without also planning for spending cuts, that doesn’t add up. And in a tight election campaign in which the Conservatives are trailing, he doesn’t want talk of Conservative cuts on the lips of voters.

The party’s platform did book some proposed spending trims and savings measures, but the total wasn’t that much different from the Liberals, and the descriptions of what is to be cut are just as vague.

The largest is the plan to eventually cut $10.5-billion on payments that Mr. Poilievre likes to say are for “consultants,” but are actually for professional services. That rubric includes lawyers, engineers, security guards and training programs, among others. Proposing to cut that category in half is not much more specific than promising to save a lot of money by spending less on stuff.

The Conservatives also promised to cut some spending through slashing foreign aid, the size of the civil service and the funding of the CBC. But given the disruption caused in the U.S. by Elon Musk’s Department of Government Efficiency earlier this year, the Conservatives probably fear that promises of more vaguely identified cuts could summon thoughts of Mr. Musk with a chainsaw.

Perhaps none of the fiscal details will make a difference to the outcome of the election, anyway. Political strategists for the major parties tend to view platforms as required but unlikely to sway voters, and assume that most don’t get deep into the numbers.

But the costing plans are a test of each party’s fiscal credibility. And overall, this year’s suggest wide differences not just in economic policy but outlook.

Mr. Carney’s Liberals pledge to spend on infrastructure and industry supports to get through a trade war and stave off recession. Mr. Poilievre’s Conservatives propose tax cuts and energy-sector deregulation to make the economy boom, don’t bother much with industrial strategy and don’t worry that the economy could be in danger.

The Conservatives’ numbers don’t include wiggle room or a recession. Their platform doesn’t just base their figures on the economy avoiding recession for the next four years, but banks on a boom.

The Conservatives count on their policies being surprising game-changers and going exactly as predicted, so the deficit shrinks by itself.