Voters in three ridings in Ontario and Quebec are heading to the polls today to elect new MPs.

The votes are expected to give the Liberals a majority of seats in the House for the first time since 2019.

That was only possible after five opposition MPs crossed the floor to join Prime Minister Mark Carney’s governing caucus.

If — as widely expected — the Liberals retain the Toronto ridings of University-Rosedale and Scarborough Southwest, they will have 173 seats.

That’s a crucial benchmark that goes beyond the 172 needed for a bare majority. One of those Liberals seats is held by Speaker Francis Scarpaleggia, who only votes in the case of a tie. Having 173 seats means the Liberals won’t need to rely on the speaker to win votes, and could allow the party to use the majority to reconfigure the composition of committees.

As it stands now, the Liberals can be outvoted at committee by Bloc Quebecois and Conservative MPs. But after tonight’s vote, the Liberals could vote to change that to give themselves a majority on every committee.

Government House Leader Steven MacKinnon told iPolitics on Saturday that the Conservatives are still slowing down the work of the government, including at committee, pointing to efforts from the Tories to slow passage of the Liberals’ anti-hate bill.

The impasse over C-9 at the justice committee was only resolved after the Liberals moved a motion in the House to fast-track its passage, which won the backing of the Bloc Quebecois.

iPolitics reported earlier this month that there appears to be frustration from the Liberals on the slow pace of government bills in Parliament.

While having a majority in the House will give the Liberals the opportunity to change the composition of committees, the Senate is a different question.

Despite over a decade of Liberal governance, the lack of a government caucus in the Upper Chamber has made it tough to predict the results of votes in the Senate.

Some sources suggested a recent report of Tom Pitfield’s potential appointment as the government Senate leader represents an effort to speed up passage of legislation in the chamber, citing complaints from the Liberal government on how senators are dealing with government bills.

The other byelection is being held in Terrebonne, a Montreal suburb that was decided by a single vote in last April’s election. It’s expected to be a much closer contest than the ones in Toronto, with the Liberals hoping to fend off a challenge from the Bloc.

It could also mean a late night of ballot watching. The Longest Ballot Committee has coordinated the nominations of several independent candidates in the riding as part of a protest to encourage electoral reform. As a result, Elections Canada is using write-in ballots only, which should slow down the counting process.

For tonight, QP Briefing’s Barbara Patrocinio will cover the votes for us in Toronto, while iPolitics‘ Aya Dufour is on the ground in Terrebonne.

iPolitics‘ editor-in-chief Marco Vigliotti is helming the liveblog from Ottawa.

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Updates will appear below.