Conservative MP Crosses Floor, Pushing Carney's Liberals Closer to Majority

A four-term Conservative MP who once sought her party's leadership crossed the floor Wednesday to join Mark Carney's Liberal government, leaving the prime minister one seat away from a parliamentary majority he has been building through defection rather than the ballot box.

Marilyn Gladu, the MP for Sarnia-Lambton-Bkejwanong in southern Ontario, became the fifth opposition member and fourth Conservative to join Liberal ranks since the April 2025 general election, pushing Carney's seat count to 171 in the 343-seat House of Commons. A majority requires 172, a threshold the Liberals could cross as soon as Monday, when three byelections are scheduled.

The irony of Gladu's switch was hard to miss. As recently as January, she praised a Conservative colleague for resisting Liberal recruitment, commending MP Amarjeet Gill for "being true to the voters who elected you," and told a local outlet that any MP who changed parties should face an immediate byelection. Conservative Leader Pierre Poilievre seized on that record, saying Carney was "seizing a costly Liberal majority that voters denied him, and doing so through backroom deals," and called on Gladu to face her constituents.

A chemical engineer with decades of experience in global supply chains, Gladu framed her decision in terms of Sarnia-Lambton's economic exposure to U.S. trade pressures. She said Carney had invited her to "bring my experience, my talents and my views into the large Liberal tent," adding the move would "have better effect inside than it will outside." Her riding sits along the Ontario-U.S. border in a region the Conservatives swept in 2025. Her defection places a Liberal vote squarely inside that belt.

The transition carried a personal dimension. Artificial Intelligence Minister Evan Solomon, the former CTV host who had interviewed Gladu about floor-crossing byelections just months earlier, was present when Carney welcomed her into caucus. A government source confirmed Solomon held "lots of productive conversations" with Gladu over recent months.

Carney framed the defections in national terms, telling reporters in Ottawa that "the country as a whole is uniting" and calling on Parliament to follow suit. A majority would give him a freer hand to advance his budget, housing agenda, energy policy, and trade posture toward Washington without negotiating every confidence vote with opposition parties. Gladu cited those same priorities, saying she wanted to help Carney's vision of diversifying trade, building homes, creating jobs, and strengthening Canada's defences.

The pattern began in November 2025: Chris d'Entremont of Nova Scotia, Michael Ma from the Greater Toronto Area, and Matt Jeneroux from Edmonton all left the Conservative benches, and former NDP MP Lori Idlout of Nunavut followed in March. Five floor crossings in five months have turned a seemingly durable minority into a government perpetually on the edge of outright control.

Three byelections on April 13 will determine whether Carney crosses that edge on his own terms. The Liberals need only one of the three seats. Toronto's University-Rosedale and Scarborough Southwest are considered safe Liberal territory. Terrebonne, Quebec, where the Liberals won by a single vote in 2025 before the Supreme Court annulled the result, is the wildcard.

For the Conservative Party, the cumulative losses pose a strategic problem that extends beyond the seat count. Poilievre's confrontational approach to opposition has not prevented five of his members from deciding they could do more work inside Carney's tent. With Monday's byelections potentially settling the majority question, the Conservatives face the prospect of opposing a government that has spent five months quietly absorbing their own.