Here’s the draft of a letter Justin Trudeau should be writing to Donald J. Trump. “My commendations, Mr. President, on your progress at the North Korean summit. Even more compliments for what you did at the G7 I hosted. My gratitude knows no bounds. You’ve revitalized my flagging leadership.

“On the foreign stage I was being depicted as lighter than a balloon. Traipsing around India in a Sherwani and local headgear didn’t help. Now, thanks to you, I’m the gallant defender of my country and the western alliance.

“You’ve brought me applause from all Canadian quarters, even from Conservatives like Stephen Harper who took to Fox News to tout my position. An all-party resolution was passed in the House of Commons in my favour.

Story continues below advertisement

“We’ve been politically polarized up here but your actions are bringing us together, kindling a national spirit. We finally have a broad consensus on something. You.”

If Mr. Trudeau were to actually put down such thoughts, he wouldn’t be far off the mark. Nothing brings a country together like a common enemy, an external threat to its well-being. Canadians are rallying around the flag. The American bully and his bloodhounds are the cause. Their calumnies, their accusations of Mr. Trudeau being a backstabber, of there being a special place in hell reserved for him, constitute, as Brian Mulroney put it, a historic low.

”I’ve never seen language like this.” said the former Tory prime minister. “Least of all from subordinates of the President directed at the Prime Minister of their greatest friend and ally.”

While what happened at the Quebec G7 meeting is potentially disastrous for Canadian trade, while Mr. Trudeau’s words at the windup news conference could have been more diplomatic so as to evade the President’s rancour, the focus is not on those questions. It is on a President Canadians loathe. Animosity had been building toward him. The G7 dispute took it to the breaking point.

The clash there might well mark an iconic moment in Canadian-American relations, one which could recast the political narrative. Relations with Washington have weighed heavily on Canadian politics. The Liberals’ record shows three elections lost as a result of getting it wrong on trade with the Americans. In reshaping the Trudeau image, Mr. Trump may have just won one for them.

What he has done is given the Prime Minister a ton of Teflon in the fight ahead. Given that the Canadian economy is five times more dependent on exports to the United States than vice-versa, it isn’t a fair fight to begin with. Mr. Trudeau is powerless to stop the President should he decide to impose tariffs on auto imports or dump North American free-trade agreement.

But Mr. Trump is now solely targeted for deteriorating conditions and will continue to be unless he reverses direction. His erratic nature makes him capable of that, though it would be a stunning shift given the extent of his wrath and his long-time commitment to America First protectionism.

Story continues below advertisement

The 1911 election was lost by the Wilfrid Laurier Liberals over a bid to carve out a free-trade deal with the administration of William Howard Taft. Incendiary remarks by Republican lawmakers that such a deal would lead to annexation fired up nationalist passions against reciprocity north of the border.

Mackenzie King went down in the 1930 election to R. B. Bennett in large part because he did not react strongly enough to the introduction of protectionist tariffs. Bennett promised to “blast” Canada’s way into other markets. The blasting never happened but that’s another story.

In the 1988 election came another confrontation over cross-border commerce that turned the tide. The Mulroney Tories won the fight for free trade against John Turner’s Liberals.

Given the extraordinarily difficult circumstances, Mr. Trudeau’s management of the American file along with Foreign Affairs Minister Chrystia Freeland and Washington ambassador David MacNaughton has been smart. It is now seen as stalwart.

At the G7 summit where he was trying to have it both ways in combining criticism of Mr. Trump with nice-guy hand pumps, Mr. Trudeau got lucky. The Trump team’s vociferous reaction jolted Canadian pride. It had the effect of putting the Prime Minster on a pedestal as the protector of the country’s valour.

A judicious playing of that patriot role, of bulwark against a villain President, could take him all the way to victory in 2019.