It's set to be the most acrimonious world summit in years, with President Donald Trump facing off against six other leaders in need of a standard-bearer.
If Justin Trudeau is looking for a chance at redemption, this is it.
With the world on the brink of a trade war, the stakes are high for when the Group of Seven meets in Canada with the symbol of postwar collaboration under threat by an aggressive strain of American unilateralism that's ripped up international agreements and undermined multilateral institutions.
Enter Trudeau, the photogenic prime minister whose brand of "progressive" trade has fallen flat amid foreign flops that wounded his image.
In private conversations, some G7 officials express reservations about the 46-year-old. They may have little choice than to embrace him.
As host, he's in the spotlight to somehow salvage a summit pitting irate Europeans against Trump with Japan's Shinzo Abe falling in the middle.
France and Germany are warning they won't bow to Trump just to show unity, while many wonder if the US president will leave early.
In the past, Trudeau tried being a Trump whisperer. But his year of diligent appeasement ultimately failed.
Tariffs hit Canada, along with everyone else. Trudeau has finally quit playing nice with Trump.
"I expect a very acrimonious summit," says Jacob Kirkegaard of the Peterson Institute for International Economics inWashington.
"Nothing of substance to be agreed. In fact, I think the best you can hope for is for them to agree to continue talking."
Trudeau "needs to clearly adopt a different style because he has found out, just like Macron did and just like Abe did, that all this personal chemistry, cosying-up bromance stuff didn't get them anywhere," Kirkegaard says.
The star power has faded for Trudeau, the son of a former prime minister. At home, his polling lead has evaporated on the heels of a disastrous trip to India, and he trails the main opposition party in polls ahead of an election next autumn.
Abroad, a French official was at pains to play down the much-talked about bromance between Emmanuel Macron and Trudeau on display at the G7 in Italy a year ago.
If the two men were being endlessly compared to one another last year, comparisons now are not welcome, the official said on condition of anonymity. Macron is focusing on developing his own brand and a direct channel to Trump.
Macron began his trip to Canada by visiting Trudeau in Ottawa, and emerged with a warning for Trump.
"None of us are eternal," Macron said. He later tweeted: "The American President may not mind being isolated, but neither do we mind signing a 6 country agreement if need be."
Trump responded on Twitter after the meeting of the two other leaders, which included a lengthy private dinner: "Please tell Prime Minister Trudeau and President Macron that they are charging the US massive tariffs and create non-monetary barriers," he wrote. "Look forward to seeing them tomorrow."
In a follow-up tweet, Trump accused Trudeau of "being so indignant" given that Canada protects its dairy sector with high tariffs.
Yesterday, Trump tweeted that if he was unsuccessful at "straightening out" unfair trade deals, "we come out even better!"
When asked for a response to Trump's remarks, a senior Canadian official at a press briefing in Quebec said the countries can manage their differences through discussions.
Trump's treasury secretary Steven Mnuchin was painfully singled out a week ago at a gathering of G7 finance chiefs in the ski-resort town of Whistler. Who knows how Trump, who dislikes criticism, will respond to coming under fire.
White House economic adviser Larry Kudlow has made it clear Trump isn't planning to woo the bloc's leaders.
"International multilateral organisations are not going to determine American policy, I think the president's made that very clear," Kudlow said.
Either way, there is the risk that it ends without the typical negotiated leaders' consensus communiqué.
Previous summits have issued a chair's summary instead, which would fall to Trudeau. If the Canadian can find any measure of consensus, that will be considered a success given the low expectations.
Trump was planning to depart the summit this morning, leaving a deputy assistant in charge for the day's remaining sessions.
"The G7 is fundamentally a gathering of the world's most advanced economies to talk about economic challenges that we have in common," Trudeau said last week in Toronto.
The key to diplomacy is finding common ground, he said. That incidentally, is also the title of his 2014 autobiography.