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Liberal MP Nate Erskine-Smith said Wednesday he will stay on as a member of Prime Minister Mark Carney’s caucus until the provincial race is called, citing crucial votes for the minority government as the reason.Spencer Colby/The Canadian Press

Liberal MP Nate Erskine-Smith says he’ll resign his federal seat as soon as a provincial by-election is called in the Toronto riding of Scarborough Southwest, although Ontario Premier Doug Ford hasn’t yet set a date for the race.

Mr. Erskine-Smith’s leap into provincial politics sets the stage for his presumptive run to lead the Ontario Liberal Party – a move that will have reverberations at Queen’s Park, where Mr. Ford hopes to win a fourth term.

The provincial vacancy in Scarborough Southwest was triggered by the surprise resignation of Doly Begum, who was the Ontario NDP’s deputy leader. Ms. Begum was named on Tuesday as the Liberal candidate in the federal riding of the same name, which was vacated this week by ex-minister Bill Blair, who resigned to become Canada’s next high commissioner to the United Kingdom.

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Mr. Erskine-Smith said Wednesday he will stay on as a member of Prime Minister Mark Carney’s caucus until the provincial race is called, citing crucial votes for the minority government as the reason.

“As soon as Doug Ford calls the by-election, I am all in. I’ll be resigning a seat here,” he told reporters in Ottawa.

“In the meantime, look [at] what’s at stake here in Ottawa. Every vote counts.”

Once the Speaker has received the official warrant that the provincial seat is vacant, Mr. Ford has six months to call the by-election, and the vote could be held in March at the earliest and September by the latest, according to Elections Ontario.

Mr. Ford said Wednesday he hasn’t decided on timing.

“I really like Doly, actually, I think she’ll do a good job as a federal MP if she’s fortunate enough to win. And I guess there will be a time to call a by-election after that, I’m just not too sure when,” Mr. Ford told Global News after an event in Mississauga.

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Asked about the prospect of taking on Mr. Erskine-Smith in the riding, Mr. Ford said, “I’ll just work as hard as we can. And hopefully we can turn that seat.”

Ms. Begum on Wednesday also clarified some of her recent comments criticizing Mr. Carney’s policy on the Middle East, which were denounced by the Centre for Israel and Jewish Affairs. Speaking in the Ontario legislature in November, she said the federal government must find its “moral backbone” and stop sending arms to Israel and “enabling this genocide.”

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Doly Begum was first elected as a provincial New Democrat in 2018.Cole Burston/The Canadian Press

In a statement to The Globe and Mail sent by the federal Liberal Party, Ms. Begum said that like many Canadians, she has been horrified by the catastrophe in Gaza.

“At times, I have felt that governments in Canada and others throughout the world did not move quickly enough to react and I have spoken directly about that,” she said.

“At the same time, I have seen Mark Carney’s new Liberal government strengthen Canada’s engagement in the region and come forward with meaningful humanitarian aid while advocating for a just and lasting peace.”

Ms. Begum, a health care and community advocate, first won her Scarborough seat in 2018. The Progressive Conservatives have repeatedly finished second there during their eight years in power, followed by the Liberals in third – although the Liberals previously held the seat when they were in government.

While Mr. Erskine-Smith, who currently represents the neighbouring federal riding of Beaches-East York, says he intends to run provincially, it is still unclear whether the Ontario Liberals will hold an open nomination race or appoint their candidate.

“No decision has been made to date on if there will be an open nomination or an appointment for the SSW [Scarborough Southwest] candidate. At this time, the party remains focused on releasing the details of our leadership race, which will be coming by Monday,” said Madalyn Calzavara, executive director of communications and legislative affairs for the Ontario Liberal caucus.

NDP Leader Marit Stiles told The Globe in an interview on Wednesday she had no indication that Ms. Begum was going to leave her party, calling it a “difficult moment.”

She said the NDP will continue to represent Scarborough Southwest in the interim and is planning a “rigorous candidate search,” pledging open nominations.

“The NDP has deep roots in Scarborough Southwest,” she said, noting that former leader Stephen Lewis represented the area in the 1960s and 70s.

The federal Liberals bypassed the nomination process when they appointed Ms. Begum as well as with Danielle Martin, a physician who is set to run in former cabinet minister Chrystia Freeland’s Toronto riding of University-Rosedale.

Those two by-elections have yet to be called, although Mr. Erskine-Smith told reporters Wednesday he believes they will happen quickly.

With a report from Emily Haws in Ottawa