The byelections will be held to replace three MPs who have chosen to leave federal politics, including former Liberal cabinet minister Marc Garneau (Notre-Dame-de-Grâce–Westmount, in Quebec), Conservative MP Dave MacKenzie (Oxford, in Ontario) and former Conservative interim leader Candice Bergen (Portage–Lisgar, in Manitoba).

A race will also be held to fill a Manitoba seat left vacant by the death of former Liberal cabinet minister Jim Carr in Winnipeg South Centre.

All four seats are generally considered safe districts for the parties who most recently held them. Winnipeg South Centre was the closest contest in the 2021 federal election, with Carr carrying the riding by about 18 percentage points.

Another seat, Calgary Heritage, remains vacant, with a byelection expected to be called after the conclusion of the Alberta provincial election.

Not all parties have announced who will be contesting the byelections, but here's what we know so far about the races:

Notre-Dame-de-Grâce–Westmount (Que.)

Former cabinet minister and astronaut Marc Garneau, 74, resigned his seat in the House of Commons in March, having represented his Quebec riding since 2008. Garneau also served in various cabinet positions since 2015, and ran for the Liberal leadership in 2013.

The Montreal riding is a Liberal stronghold, and the Liberal candidate, to be announced Monday, should be seen as the favourite to win the byelection.

Marc Garneau, a longtime Liberal MP, cabinet minister and former astronaut, retired in March. (Adrian Wyld/The Canadian Press)

The New Democratic Party has two candidates for the nomination, with no nomination date yet set:

• Jean-François Filion: An English teacher at Westmount's École International and a member of the NDP's Quebec committees for relations with Indigenous nations and the environment.
• Malcolm Lewis-Richmond: A longtime NDP member who is currently taking on the Liberal government as part of the Professional Institute of the Public Service of Canada's bargaining team.

Oxford (Ont.)

After two decades as the Conservative MP in Oxford, Dave MacKenzie, 76, announced his retirement in December, standing down in late January.

The safe Conservative riding in rural southwestern Ontario hasn't elected a Liberal since 2000, and recently featured a divisive nomination battle — with allegations that Conservative Leader Pierre Poilievre and former leader Andrew Scheer were interfering in the race to the advantage of the eventual candidate, Arpan Khanna. Khanna was a senior member of Poilievre's leadership campaign team.

The Conservatives' candidate selection committee voted in March to disqualify Gerrit Van Dorland from seeking the nomination in Oxford.

RightNow, an anti-abortion group working to elect MPs that share their views on abortion, has cried foul, claiming Van Dorland was disqualified because of his views on the issue.

A Conservative Party spokesperson said in a media statement that Van Dorland was disqualified because he failed to disclose required information during the candidate application process.

In an unusual move, MacKenzie has since come out publicly in support of Liberal David Hilderley, who is seeking the Liberal nomination in Oxford. The Liberals will announce their candidate on May 15.

Cody Groat, an assistant professor in history and Indigenous studies at Western University in London, Ont., has been confirmed as the riding's NDP candidate.

Portage–Lisgar (Man.)

Former interim Conservative leader Candice Bergen, who served as MP for the Manitoba riding of Portage-Lisgar since 2008, resigned her seat in the House of Commons in February.

Bergen, 58, served as interim leader of the Conservatives and Opposition leader from February to September 2022. Prior to that, she served as deputy leader of the Conservatives.

Branden Leslie, Bergen's former campaign manager, was nominated as the party's candidate earlier this month, beating out Cameron Friesen, a longtime Manitoba MLA for the provincial riding of Winkler-Morden.

 Candice Bergen, who served as interim leader of the Conservatives, resigned her seat in the House of Commons in February. (Sean Kilpatrick/The Canadian Press)

People's Party of Canada Leader Maxime Bernier, a former Conservative cabinet minister in Stephen Harper's government, has announced that he will run in the riding to try to wrest the deep blue seat from the Conservatives.

Bergen easily won the riding in 2021, winning more than 50 per cent of the vote. The People's Party of Canada candidate came in second with 22 per cent of the vote.

Kerry Smith, a senior director in the Manitoba Métis Federation, is the Liberal candidate in Portage-Lisgar.

The NDP has not announced a candidate for the riding yet.

Winnipeg South Centre (Man.)

Former Manitoba MP Jim Carr, who represented Winnipeg South Centre since 2015, was diagnosed with multiple myeloma — a type of blood cancer — the day after he was re-elected on Oct. 21, 2019. He also suffered kidney failure.

Two months after Carr passed away on Dec. 12 at the age of 71, his son, Ben Carr, announced that he will be seeking the Liberal nomination in the riding his father won on three occasions.

Ben Carr, Jim Carr's son, speaks at his father's memorial service on Dec. 17, 2022. Carr is running to take over his late father's seat in Parliament. (John Woods/The Canadian Press)

Carr, who was confirmed as the party's candidate in April, has a strong chance of becoming the next MP for the Winnipeg riding, a reliable but not exclusive Liberal seat.

The NDP has nominated Julia Riddell, a clinical psychologist, to run in the riding. Riddell, who was acclaimed in the nomination race, works in the public health-care system and teaches at the University of Manitoba.

The Conservatives have nominated Damir Stipanovic, who has worked as an air traffic controller and in the Royal Canadian Air Force Reserve, to run in the riding.