Conservative commentator and vocal Donald Trump critic David Frum will square off against Steve Bannon in Toronto tonight as part of a debate that has drawn criticism for giving a platform to the U.S. president's controversial former chief strategist.

The two will be facing off against each other as part of the Munk Debates, where they will argue over the rise of populism, and whether the "surging populist agenda in Western nations signal a permanent shift in our politics" or if it's a "passing phenomenon that will remain at the fringes of society and political power."

Bannon, an advocate of right-wing populism, will support the proposition that "the future of Western politics is populist not liberal."

Years before he became Trump's strategist, Bannon told journalist Ronald Radosh, he wanted "to bring everything crashing down and destroy all of today's establishment."

Frum, the author of Trumpocracy: The Corruption of the American Republic, will make the counter-argument, and shortly after announcement of the debate, Frum tweeted he will argue that Bannon's politics "will lose and liberal democracy [will] prevail across the Western world."

'Democratic ideas can defeat him'

For good or ill, Frum described Bannon as a "key intellectual leader of the severest challenge liberal democracy has faced since the fall of communism."

"Mr. Bannon comes to the prestigious Munk platform because he believes his words can persuade people to follow him," Frum said. "I will face him there because I believe democratic ideas can defeat him."

Although both hail from the right of the political spectrum, Frum, currently a senior editor of The Atlantic magazine, has been frequently frustrated by the Republican Party and is a vocal critic of the Trump administration.

Bannon champions economic nationalism and anti-globalism. But he has also been accused of fuelling racist, misogynistic and anti-Semitic views, in particular while chairman of the far-right Breitbart News Network, which he once described as "the platform for the alt-right."

Bannon has denied that he is a white nationalist and that the anti-establishment alt-right movement is inherently racist, although he has conceded it may attract racist, anti-Semitic and homophobic elements.

As Trump's chief strategist and the man credited for overseeing the U.S. president's victory, Bannon, for a time, held a significant position of power. But things began to unravel soon after he departed the White House last year.

He rejoined Breitbart News but was forced to step down as CEO earlier in January after his criticisms of Trump and his family were published in a book by author Michael Wolff.

He has since been travelling through Europe, trying to drum up support for a new organization, The Movement, that seeks to advise and advocate for right-wing populist parties across the continent.

Dropped by New Yorker

Bannon recently made headlines after the New Yorker, which had planned to interview Bannon at the magazine's annual festival, dropped him following outrage over his attendance.

Now in the wake of the Pittsburgh synagogue massacre that left 11 dead, critics — including the federal NDP and a coalition of more than 40 community groups advocating against racism — are calling for tonight's debate to be scrapped.

The coalition opposes the presence of both Bannon and Frum, a former speechwriter for George W. Bush, who has come under criticism in the past for his role in that administration and its controversial decision to invade Iraq in the wake of the 9/11 terrorist attacks.

Bannon was chief strategist for Donald Trump and is largely credited for overseeing his victory. Frum, on the other hand, has been a vocal critic of the U.S. president and his administration. (Manuel Balce Ceneta/Associated Press)

New Democrat MP Charlie Angus said it wasn't "acceptable to give provocateurs like Mr. Bannon the opportunity to present their extreme views."

Protests and rallies are expected at the event, taking place in downtown Toronto's Roy Thomson Hall in front of an audience of 3,000.

'Providing a public service'

Rudyard Griffiths, the chair of the Munk Debates, has defended the event, saying it's "providing a public service by allowing their ideas to be vigorously contested and letting the public draw their own conclusions from the debate."

"Civil and substantive public debate of the big issues of our time helps all of us better understand the challenges we face as a society and what, if anything, can be done to resolve them," he said.

The debate will be streamed live on the Munk Debates website and Facebook page at 7 p.m. ET and air live on CPAC.