When Donald Trump jokes that Canada could become the 51st state, and refers to Justin Trudeau as a governor rather than prime minister, it's all an effort to "humiliate" the Canadian leader, a former senior Trump adviser says.

And it's to be expected from the U.S. president-elect, said John Bolton, who's now a Trump critic.

"I think he's poking at Justin Trudeau and trying to humiliate him, and I think Trump gets a laugh from it."  

On Trump's jokes about Canada, and quips aimed at the prime minister, Bolton says, "I wouldn't over-intellectualize it. I think he's just mean."

While Bolton is not a Trump supporter, he knows how the incoming president thinks and strategizes: He served as Trump's national security adviser for roughly 17 months during his first term. He says he quit in 2019, after clashes over foreign policy strategy. At the time, Trump said he fired him. 

In interviews with CBC News, Bolton and several U.S. senators also spoke about the need for Canada to play into the president-elect's ego, and what can be done to try and avoid a trade war.

Canada as the 51st U.S. state?

Trump has made at least four recent references to Canada becoming a U.S. state, sparking a wide range of reactions.

And according to Gerald Butts, Trudeau's former principal secretary, this has actually been going on for years: "Trump used this 51st- state line all the time with Trudeau in his first term," he wrote in a social media post.

Trump appears to have picked up where he left off, starting with his dinner with Trudeau at Mar-a-Lago, held after the president-elect, in an online post, threatened a 25 per cent tariff on all Canadian and Mexican goods.

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As first reported by Fox News, Trump appeared to joke that Canada could become the 51st state if the Canadian economy were to be destroyed in a tariff fight. 

He seemed to reference that quip on his social media account days later, posting what appeared to be an AI-generated image of himself standing atop a mountain with a Canadian flag.

He said it again during an interview with NBC News, as he complained about trade deficits with both Canada and Mexico.

After characterizing trade deficits as subsidies, he said, "If we're going to be subsidizing them, let them become a state."

And then there was the Truth Social post, around midnight Monday, where Trump made reference again to his Florida meeting with Trudeau.

Trump's comments are getting some laughs on Capitol Hill. 

Republican Senator Josh Hawley, who represents Missouri, chuckled as he told CBC News he's not quite sure why Trump keeps talking about Canada becoming a state.

"I like better his idea of splitting Canada up into two — admitting one Republican and one Democrat state," he quipped. 

"I wouldn't want a 51st state if they're just going to vote for Democrats."

Stay out of U.S. domestic politics: Bolton

Bolton says Trudeau and the Canadian team responding to Trump's tariff threats need to play into the president-elect's ego. 

"I think it's important in dealing with Trump to make the case not why the threat will hurt Canada, but why not invoking the tariffs will help Trump," he said.

"Forget about U.S.-Canadian relations, that's not the issue for Trump — what makes Donald Trump look good?" 

• This Sunday, Cross Country Checkup is asking: What do you make of all the Trump jokes? And, should Canada be America's 51st state? Fill out this form and you could appear on the show or have your comment read on air.

He also criticized Trudeau for weighing in on the outcome of the presidential race. In Ottawa on Tuesday evening, the prime minister told a crowd that Kamala Harris's U.S. election loss was a setback for women's progress.

"If Prime Minister Trudeau hasn't figured it out, I'm happy to offer some free advice: Don't get involved in the middle of American politics, it's not going to do ya any good," Bolton said. 

Tariff threats real, some Republican senators say

Some Republican senators warn that Trump may very well make good on his tariff threat.

"Oh, I think he's serious about it, for sure," said Senator Kevin Cramer, during a brief interview with CBC News in the hallway of the Hart Senate Office Building on Capitol Hill. 

Cramer, who represents the northern border state of North Dakota, urged officials in Ottawa to meet Trump's demands.

"We just need to get compliance and we'll be fine."

Trump has linked the threat to broad changes in border security, to prevent the flow of migrants and illegal drugs into the U.S. He's lumped challenges at the southern and northern borders together, despite very different circumstances. 

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Following a meeting with Prime Minister Justin Trudeau and Canada's premiers on Wednesday, Ontario Premier Doug Ford said Canada needs to be 'ready to fight' and that Trump's tariffs are '100 per cent' coming. International trade expert Wendy Wagner discusses how Canada's measures could be harmful for not only Americans, but Canadians, too.

And he hasn't provided specifics to either Canada or Mexico about what exactly he'd like to see changed. 

One Republican strategist says Canada needs to just focus on the tariff threats, and ignore what he calls Trump's "nonsense."

"No one is expecting Canada to become the 51st state," said Matthew Bartlett, who worked in the State Department during the first Trump administration.

"Donald Trump is a master showman, loves to command people's attention, loves to make people nervous and keep them on their toes. That's one of his tactics."

Bartlett predicted four years of quips and threats.

Bolton says Trump has a fixation with tariffs, and refuses to accept they will likely make life more expensive for American consumers. 

"Tariffs are paid by the American importer, and then ultimately the bulk of the tariff is probably passed on to American consumers.… Trump doesn't get it," he said.

"It's like arguing the Earth is not flat. You're not going to persuade him."