Canadian history is dotted with floor-crossers. Voters haven't always been thrilled

Traitor, shameful, brave, principled.

There’s a spectrum of terms used to describe MPs who cross the floor. But history shows us there’s one word that doesn’t always stick when Canadian politicians shed one party affiliation for another: re-electable.

Jaws dropped in Ottawa following the revelation that longtime Conservative Chris d'Entremont is joining the federal Liberal caucus — with Prime Minister Mark Carney hinting others could follow.

Floor-crossing is a political phenomenon dating back to Confederation. But a dive into the record books shows it has increasingly come at an electoral price. 

“Switching parties is an extremely risky move that almost always hurts a politician's chances of re-election,” said Semra Sevi, assistant professor in the University of Toronto’s political science department. 

She tracked every MP who switched parties from Confederation to 2015. The paper found that up until the mid-20th century, floor-crossers received nearly the same vote share in the election immediately after they changed parties as the one before.

But since the 1970s, their fortunes have declined, she said.

“As parties become institutionalized, the electoral cost of switching has rose dramatically. So that makes political survival outside of one's party increasingly unlikely,” Sevi said.

“There are rare instances of success. So time will tell if this will be one of them."

Over the years, hundreds of MPs have changed affiliations — some sit as an Independent or start their own party, while some of the most memorable cases involve joining their former rivals.

Sevi said an MP's chances of getting re-elected after changing parties often depend on whether voters buy their reasons.

D'Entremont said he no longer felt represented in Conservative Leader Pierre Poilievre's party and pointed to his "negative" approach to politics.

“Switching is often seen as opportunistic, so it harms credibility,” Sevi said. 

“This is a switch that is happening about seven months after the election was held. So it really depends if the voters in his constituency agree or not [with] his reasons.”