OTTAWA—Byelections will be held on April 3 to fill five vacant federal ridings, but the contests are unlikely to change the partisan math in the House of Commons.

Of the five byelections called by Prime Minister Justin Trudeau, two are among the safest Conservative seats in the country and are likely to remain so: Calgary Heritage, former prime minister Stephen Harper’s old stomping ground, and Calgary Midnapore, formerly held by one-time Harper minister Jason Kenney, who is now running for the leadership of Alberta’s Progressive Conservative party.

The other three — the Montreal riding of Saint-Laurent, the Toronto-area riding of Markham-Thornill and Ottawa-Vanier — are Liberal strongholds and likely to stay that way.

Saint-Laurent and Markham-Thornhill were left vacant last month after veteran Liberal ministers Stéphane Dion and John McCallum were named to plum diplomatic posts as part of a cabinet shuffle.

Read more: Five byelections won’t be a test of Trudeau but do mark end of an era: Hébert

Ottawa-Vanier has been without an MP since last August when veteran Liberal Mauril Belanger died from amyotrophic lateral sclerosis.

New Democrat MP Matthew Dube said the byelections are a chance for opposition parties to remind Canadians of all the promises Trudeau has broken since his 2015 election victory, such as abandoning his vow to reform the country’s voting system.

And Conservative MP Gerard Deltell said the fact that Dion was evidently forced out of cabinet against his will — the former Liberal leader took several weeks to finally accept Trudeau’s offer to make him ambassador to Germany and the European Union — might provoke a backlash among voters in Saint-Laurent.

“Maybe this is an opportunity for people to express themselves, that they are not very happy in the way Mr. Trudeau paid tribute to Mr. Dion,” Deltell said. “It’s not the way to end a so great political career.”

Indeed, back in 2002, the Liberals lost two ridings they’d held for decades — Windsor West and Gander-Grand Falls — after then-prime minister Jean Chretien cleared space for fresh faces in his cabinet by giving appointments to veteran Grits Herb Gray and George Baker. Windsor voters in particular were angry over what was widely perceived as Chretien’s disrespectful treatment of Gray, who had held the riding for almost 40 years.

But while byelections can be unpredictable, there are unlikely to be any surprises this time.

Notwithstanding some stumbles in the first 16 months of his mandate, including the so-called cash-for-access fundraising controversy, Trudeau and his government remain comfortably ahead in opinion polls. And the Liberals’ two main rivals, the Conservatives and NDP, are in the midst of leadership contests that will not be concluded before April 3.

Moreover, the history of the five ridings suggests voting patterns in each are firmly entrenched.

Ottawa-Vanier has elected nothing but Liberals since its creation in 1935. Belanger won the riding in 2015 with almost 58 per cent of the vote.

Similarly, Saint-Laurent has elected only Liberals since its creation in 1988. Dion took almost 62 per cent of the vote.

In Markham-Thornhill, a new riding as of the 2015 election, McCallum won with almost 56 per cent of the vote.

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The two Calgary ridings were also newly redrawn for 2015 but the city generally has been an unassailable Conservative fortress for decades. While the Liberals made modest inroads in the last election, picking up two Calgary seats, Harper won his riding with almost 64 per cent of the vote and Kenney took his with 67 per cent.

Currently, the Liberals have 180 seats in the 338-seat Commons. The Conservatives hold 97, the NDP has 44, there are 10 Bloc Québécois members, one Green party member and one independent.

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