OTTAWA - A familiar U.S. face finally showed up front and centre on the federal campaign trail Saturday: Donald Trump.

NDP Leader Jagmeet Singh promised to go toe-to-toe with the mercurial, unpredictable American president just as Justin Trudeau's Liberals released a new English-language ad touting their own record in confronting the White House during last year's tension-fraught NAFTA talks.

“You fight a guy like that - you just don't back up, you don't back down,” Singh said during a campaign stop in Oshawa, Ont., where he was talking about how a New Democrat government would seek to jump-start Canada's stalled auto sector.

“When it comes down to it, just because he wants to create jobs in the United States doesn't mean we should give up on jobs in Canada. And we're not going to give up on jobs in Canada.”

It just so happened that the Liberals were also thinking about unions and blue-collar workers Saturday as they debuted “Fought Tooth and Nail” - a radio and internet ad, narrated by Chrystia Freeland, celebrating the new North American trade pact and the successful end of punitive U.S. tariffs on Canadian aluminum and steel.

Trudeau, who was spending the day shaking hands with members of the public throughout Quebec, has been under sustained criticism from both Singh and Conservative Leader Andrew Scheer over how the Liberal government handled the marathon talks, which lasted nearly a year and a half.

During that time - and the preceding months, when Trump seemed to delight in bashing NAFTA at every turn - Trudeau and Freeland were careful to avoid referencing the U.S. president by name. They instead referred generally to the American administration, a strategy government officials believed would avoid provoking Trump into drastic action that would threaten the effort.

But that strategy is put through a partisan wood chipper in the English-only ad, which being deployed across in southwestern Ontario - a Canadian manufacturing heartland that had a lot at stake in the free-trade effort - but not in Quebec, where dairy farmers are decidedly less pleased.

“We stood up to Donald Trump on trade when the Conservatives wanted Canada to back down,” Freeland says in the ad over a visual of Trump greeting Trudeau at the White House. “The Conservatives told us to take any deal we could get. Capitulation is not a negotiating strategy.”

Scheer took aim at an absent-Trudeau during this week's leaders' debate, saying that Trudeau signed a deal with the United States and Mexico that hurts Canada's economic interest.

Green party Leader Elizabeth May, too, looked to use Trump as leverage over Scheer in the debate, citing a famous vaudeville puppet act to illustrate what she considers the Conservative leader's affinity for the president.

“You will do what Trump wants,” she railed. “He might as well be the ventriloquist and you're Charlie McCarthy.”

“That's just false,” Scheer replied. “I believe that we should not sign away our sovereignty on our foreign affairs, which is what Justin Trudeau did when he signed NAFTA and conceded a huge concession to the United States on future trade deals and future exports of certain Canadian products.”

The deal itself, christened by Trump the United States-Mexico-Canada Agreement, or USMCA, is awaiting ratification on Capitol Hill with no clear timelines in sight. Democrats control when the ratification bill will be introduced in the House of Representatives, and have raised issues with the wording of labour and environmental provisions.

Trade was also on Singh's mind Saturday as he delivered some Trump-style protectionism of his own: a suite of measures to keep auto jobs in the country and encourage new-car buyers to spend their money on built-in-Canada cars and trucks.

The measures, also intended to encourage Canadian consumers and businesses to opt for zero-emissions vehicles, are part of the climate-change strategy the NDP unveiled in May and which Singh was brandishing at an event later in the day at a farmer's market in downtown Kingston, Ont.

There, Singh doubled down on his anti-Trump stance, calling out the president's immigration measures at the U.S.-Mexico border, where the detention of migrants and the separation of families has been making headlines for months.

“He's done really disgusting things,” Singh said.

“We've got to call out the treatment of families: babies being ripped from the arms of mothers, that's horrible. They're fellow human beings; they should not be treated that way. The fact that Mr. Trudeau has remained silent and has not called that out is really troubling. It's wrong. You've got to call out people who are doing these types of things. Canadians expect it I'm willing to do it, I'm prepared to do it.”

The campaigns, meanwhile, are narrowing their orbits for a brief weekend respite in the national capital. Singh was scheduled to attend a rally event later Saturday in Ottawa, while Scheer was headed for a campaign event in the nearby suburb of Kanata.

Green party Leader Elizabeth May was back in her Vancouver Island riding to attend a fair before travelling to the mainland for an evening event with a local candidate, while People's Party of Canada Leader Maxime Bernier was in his Quebec stronghold of Beauce.