Who will pay for the wall? Canada.
Just as he's about to be feted in Washington by U.S. President Barack Obama next week, Justin Trudeau has to face the more-solid, post-Super Tuesday possibility that Donald Trump could be next in the White House. Republican presidents are typically unloved by Canadians but good for cross-border trade, but Mr. Trump promises he'd be a glaring exception.
That wall along the southern U.S. border that Mr. Trump pledges, and inexplicably insists will be paid for by Mexico, may be mostly about immigration, but it's also part of an isolationist and anti-trade rhetoric that's a danger signal for Canada.
Maybe Mr. Trump will moderate the isolationist bombast as he nears an election, or, if he actually wins, in office. Maybe he's just pandering to those sentiments to appeal to clearly disgruntled voters. But if that pandering helps him toward the presidency, plenty of other politicians could ride it to an isolationist Congress.
That what-if might be in the back of Mr. Trudeau's mind at a state dinner hosted by Mr. Obama next week. It's one thing to feel the love from the outgoing incumbent. But how would he deal with a Trump America?
The reset that Mr. Trudeau is touting with Mr. Obama doesn't seem likely to last with a President Trump, even if the latter says he loves Canada.
In December, when asked about Mr. Trump, the new PM said he's against "the politics of intolerance or hateful rhetoric."
His senior adviser, Gerald Butts, has been tweeting remarks about Mr. Trump, not so direct that he's attacking a presidential contender, but enough so you get the drift. He mentions the cheeky campaign suggesting Americans move to Mr. Butts's native Cape Breton if Mr. Trump is elected; after Mr. Trump failed to disavow former Ku Klux Klan leader David Duke, Mr. Butts wondered "how many people are searching the world's databases for a picture of Trump and Duke right now."
That won't upset many Canadians. Some want to bar Mr. Trump from the country. But the potential implications of Mr. Trump's rhetoric is cause for worry.
Mr. Trump hasn't just opposed the proposed Trans-Pacific Partnership trade deal, he promised to break NAFTA unless he can renegotiate it – while telling voters Mexicans are swindling the United States. He promised he'd force China to open markets wider.
To sum up: He's threatening a trade war that could disrupt trade between the world's two largest economies, and to break up the trade bloc that includes Canada and the United States.
Of course, he might not, even if he wins. Derek Burney, the former diplomat and chief of staff to Brian Mulroney, notes presidents don't have all the power in the U.S. system, and Mr. Trump might have to moderate his positions to get to the White House. Deep interests link Canada to the United States, he noted, and Mr. Trump has directed his suspicion toward Mexico, not us.
"I have to believe that the election itself will be a conditioner," Mr. Burney said. "He may not win. But even if he were to win, the constraints on any president will influence more of a common-sense direction. We've got to hope that, right?"
But the flip side is the disaster that would occur if Mr. Trump did live up to his isolationist swagger. Some see it as corollary to the protectionist wave after the 1929 stock-market crash, when the United States passed the Smoot-Hawley tariff that helped tip the world into deep depression. Mr. Burney acknowledges he harbours a worry that Mr. Trump would do what he says on trade, taking the world "back to the Thirties."
It was Mr. Burney who once argued that Mr. Obama "lost Canada," by rejecting the Keystone XL pipeline and disregarding Canadian interests. He dislikes Hillary Clinton's positions on Keystone and the TPP. He usually argues Republicans are better for Canada. But he's not willing to say the same about Mr. Trump, not unless he backtracks.
Mr. Trump would probably approve the Keystone pipeline, however; a victory for Alberta energy. For Mr. Trudeau, he wouldn't be a cross-border partner on climate change. But both could seem like details if Mr. Trump and a group riding into Congress on the same wave really do build a trade wall, because Canada would pay.