Pierre Trudeau and Richard Nixon were not kindred spirits. Nor were Trudeau and Ronald Reagan, though the Trudeau children are said to have been fond of the 40th president.

But Pierre Trudeau likely did not have much reason to worry he might wake some morning to learn he had become the target of a public tirade by the leader of the free world. And not only because Twitter did not exist at the time.

Justin Trudeau is faced with something else entirely in his meeting with Donald Trump Monday: a changeable, unrestrained president who operates outside almost all traditional norms.

He is a president who has mused of banning Muslims from travelling to the United States, has a history of disparaging women and has spoken positively of using torture to combat terrorism, and whose election has sparked fears over the fragility of American democracy and the stability of the existing global order.

And it just so happens that Trudeau prides himself on representing diversity, openness and sunny ways and has, as a result, acquired some amount of global fame in his own right.

But for all that, Trudeau and Trump are also simply the leaders of two neighbouring countries whose economies are deeply intertwined.

Prime Minister Justin Trudeau spoke to reporters in Iqaluit today 1:02

The prime minister might hope that simple reality prevails on Monday, when the two men meet each other for the first time.

It is merely everything else that seems to weigh heavily on the moment.

Trudeau billed as a 'competing voice'

In previewing Trudeau's trip to the White House on Monday, the Washington Post briefly explained to its readers that Trudeau had "begun to position himself as a Trump foe on the world stage."

Shortly thereafter, the write-up was amended so that Trudeau was merely a "competing voice to Trump on the world stage."

Such is the line that Trudeau has lately tried to walk, most famously with his tweet the day after Trump moved to ban travellers from seven Muslim-majority countries. In that case, Canadian values were asserted and the context was obvious, but neither Trump nor his policy were directly criticized.

"I'm never going to shy away from standing up for what I believe in," Trudeau tells Belleville town hall. 1:25

Two weeks earlier, Trudeau laid out an approach at a town hall in Belleville, Ont.: He would take a constructive approach, prioritizing the Canadian economy, but he would not shy away from calling himself a feminist or proclaiming the positive contribution of Muslim Canadians.

Even that much might risk Trump's pique — before that Belleville appearance, the prime minister had kept to stressing the economic imperative when asked about Trump. But Trudeau also risks seeming too timid to anyone concerned about the Trump presidency.

Officially, Monday's focus will be the economy

Things have only become more complicated since then. Refugees fleeing the United States are crossing the border into Manitoba, Muslim Canadians are being turned away by U.S. guards, the school board in Windsor, Ont., has cancelled all field trips to the United States and critics are calling on Canada to suspend its refugee agreement with the United States.

But, officially, Monday's meeting will focus on the economy.

It is comparatively easy for NDP leader Tom Mulcair to flaunt the fact that he thinks Trump is a "fascist" or for even European leaders to criticize American policy, but for the Canadian prime minister the stakes are significant and immediate, measured in jobs and trade.

All eyes are on Trudeau to set the tone with Trump’s administration. Many are saying he isn't being tough enough. The At Issue panel weighs in 12:08

With Trump wanting to renegotiate NAFTA, the Liberal government has been keen to make sure his administration understands their mutual economic concerns.

"Thirty-five states count Canada as their number one export market, and 13 others have us in their top three," Finance Minister Bill Morneau reminded an audience in Washington last week.

Morneau will be one of five cabinet ministers accompanying Trudeau to the White House, alongside Foreign Affairs Minister Chrystia Freeland, Public Safety Minister Ralph Goodale, Defence Minister Harjit Sajjan and Transport Minister Marc Garneau.

Trudeau's side has gamely argued that both governments are interested in helping the middle class. And even if not much of anything is settled in the course of a single meeting, it will be an opportunity for Trudeau to deliver a few key messages.

It will also simply be a chance for the two men to get acquainted.

"I've had the privilege of accompanying the prime minister in meetings with many foreign leaders. He is superb at communicating Canada's positions while building a personal rapport," says Roland Paris, the University of Ottawa professor who served as a senior adviser to Trudeau. "I expect that he'll do the same with Trump."

That much might be the easy part.

What happens when Trudeau and Trump appear beside each other in public?

As Japanese Prime Minister Shinzo Abe learned on Friday, even the simple act of shaking hands with the new president has the potential to become an adventure that sets social media alight.

British Prime Minister Theresa May somehow ended up holding hands with Trump. Later, at their joint news conference, she was asked to account for how she disagrees with the president. The BBC reporter who challenged May then proceeded to ask Trump how he would reassure those who worried that a man with his views was now leader of the free world.

"This was your choice of a question?" Trump chided May.

Every second of Trudeau's public interaction with Trump will be a potential source of fascination and meaning.

For sure, each meeting of prime minister and president since Confederation has been somehow significant. And any number of conflicts have arisen over the last 150 years. Pierre Trudeau was known, for instance, to have exasperated both Reagan and Nixon.

But, at least in modern times, there has never been a president like Donald Trump.

On Monday, Trudeau will come face to face with that challenge.