For starters, Trump appears aware that he’s become a factor in the Canadian election, and that he may have contributed to the Liberal Party’s extraordinary rebound. He, and people close to him, have made statements showing some awareness of those dynamics.

Another reason? Carney is not Trudeau. Trump spoke with unique disdain for the former PM, something his former aide John Bolton said Trump also did in private.

Carney also surprised some Americans with his comments yesterday about the rupture in Canada-U.S. relations, getting lots of attention in Washington.

Washington-based Canada-U.S. trade consultant Eric Miller said it has begun to dawn on people here that there could be long-term damage to a close relationship, one that benefits the U.S.

“They [realize the] need to moderate their rhetoric and keep the relationship going in a historically positive direction,” Miller said.

And finally, Americans don’t want a fight with Canada. Poll after poll shows that tariffs on Canada are unpopular, as is the 51st-state talk.

Consumer sentiment is plunging and inflation fears are at a decades-long high, so Trump has some incentives to patch things up.

“Of course, it’s one statement, one call,” Miller added. “[Trump] changes just like the weather.”

In the Westminster parliamentary system used in Canada, the legitimacy of an elected government hinges on its ability to command the confidence of the House of Commons. During an election period, the House is shut and so the prime minister cannot seek approval from the elected chamber.

Because of that, the prime minister and cabinet are directed by the convention to act with restraint, which means they shouldn't introduce big, new things or make changes that would be onerous for the next government to roll back.

This does not mean that the government is prevented from making decisions. Prime Minister Mark Carney still has the responsibility of ensuring the routine operation of the government continues and must also be able to respond to emergencies such as natural disasters, wars or economic crises.

[Former Clerk of the Privy Council Michael Wernick] says that deciding what must be done — and what should not be done — comes down to the judgment of the prime minister guided by tradition, such as ensuring government actions demonstrate respect for the democratic will of Canadians.

"There's no rule book to go to that would tell you exactly where that threshold is," Wernick said.

When it comes to responding to tariffs being imposed on Canada by the Trump administration, the prime minister and his cabinet have the power and authority they need to respond with retaliatory tariffs or help for workers.