Poilievre Loses Seventh MP Since Election as Larry Brock Quits Parliament

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A federal Conservative caucus already reshaped by defections and departures is losing another familiar face. Ontario MP Larry Brock says he will resign from the House of Commons on September 18 and return to the Crown attorney’s office in Brantford, where he worked as a prosecutor before entering politics. His planned exit makes him the seventh Conservative MP counted among departures from Pierre Poilievre’s caucus since the 2025 federal election.

Brock’s decision is different from the four Conservative floor crossings that helped strengthen Mark Carney’s Liberals, but the timing still matters. It comes after a summer of Conservative turnover, a June front-bench shuffle, and months of scrutiny over Poilievre’s ability to keep a large opposition caucus unified while rebuilding after the election loss.

Brock’s Exit Comes With a Clear Career Move

Brock is not leaving Parliament to join another party. He said he will formally resign on September 18 and return to the Crown attorney’s office in Brantford, describing the move as a return to the “front lines of justice.” Before winning a federal seat in 2021, he spent almost 19 years as a prosecutor. That background became central to his political identity, particularly as the Conservatives pressed the Liberals over bail, sentencing and violent crime.

The timing makes the announcement politically notable even if Brock’s stated reason is professional rather than partisan. The House of Commons is scheduled to return from its summer recess on September 21, meaning his resignation would take effect just three days before MPs come back to Ottawa. Poilievre publicly thanked Brock for his work on crime and victims’ issues. Brock, for his part, expressed confidence that Conservatives would retain the riding, framing his departure as a handoff rather than a break with the party.

The Seven Departures Tell More Than One Story

Brock is being counted as the seventh Conservative MP to leave, or announce an exit from, Poilievre’s caucus since the 2025 election. Four made the most politically damaging kind of move: Chris d’Entremont, Michael Ma, Matt Jeneroux and Marilyn Gladu crossed the floor to the governing Liberals between November 2025 and April 2026. Gladu’s switch was especially striking because she had been elected four times as a Conservative and became the fourth Tory defector in roughly five months.

The other departures were different. Quebec MP Richard Martel left the Conservative House caucus after Prime Minister Mark Carney appointed him to the Senate in July. Saskatchewan MP Cathay Wagantall announced that she will resign her Yorkton—Melville seat on August 31 while explicitly saying she still supports Poilievre. Brock’s September departure adds another vacancy, but not another defection. That distinction matters: seven departures do not equal seven rebellions. Still, the cumulative effect is a caucus that has experienced unusually visible turnover since voters went to the polls in April 2025.

Brock Had Become One of the Party’s Main Justice Voices

Brock’s parliamentary work was closely tied to the justice file. House of Commons records show that he has served on the Standing Committee on Justice and Human Rights since his first term and is currently a vice-chair. As Conservative justice critic, he was frequently used to challenge Liberal criminal-justice policy and advance opposition arguments on bail, sentencing and repeat violent offenders. In September 2025, for example, he sponsored an opposition motion calling for substantially tougher restrictions on people convicted of repeated serious offences.

That role changed at the end of June. In Poilievre’s June 30 critic shuffle, Oxford MP Arpan Khanna took over the justice portfolio. Reporting at the time said Brock had chosen to step back for personal reasons. The sequence is worth noting without overreading it: leaving the critic role in June does not prove he had already decided to leave Parliament, but it did reduce his front-line responsibilities shortly before the resignation announcement. His continued vice-chair role on the justice committee shows he remained active on the file even after the critic change.

His Riding Gives Conservatives a Real Cushion

The coming byelection will take place in Brantford—Brant South—Six Nations, a southwestern Ontario riding where Brock won comfortably in the 2025 general election. Elections Canada’s official results show Brock received 34,501 votes, or 52.4 per cent, compared with 27,032 votes, or 41.1 per cent, for Liberal candidate Joy O’Donnell. That was a margin of 7,469 votes, while the NDP finished a distant third with 3.7 per cent.

The broader local history also favours the Conservatives. The federal seat in the Brantford area has been represented by Conservatives since 2008, when Phil McColeman defeated Liberal incumbent Lloyd St. Amand. That does not make a byelection automatic, particularly when turnout, candidate quality and the national mood can matter more than they do during a general election. But it means the Liberals would be trying to overturn a well-established Conservative advantage rather than simply defend a swing seat. For Poilievre, holding the riding would help separate Brock’s personal career decision from the earlier caucus defections that directly benefited Carney.

Poilievre Still Has Strong Party-Member Backing

The departures create an awkward contrast with Poilievre’s standing among Conservative members. At the party’s national convention in Calgary on January 31, he won 87.4 per cent support in a mandatory leadership review, comfortably clearing the informal 75 per cent benchmark some Conservative strategists had suggested would demonstrate authority. That result gave him a clear mandate from the party base to remain leader and try again in the next federal election.

The challenge is that internal membership support and parliamentary stability are not the same thing. In the 2025 election, Conservatives won 144 of 343 seats, up from 119 in 2021, but Carney’s Liberals finished first with 169. Poilievre also lost his own Carleton seat before returning to the House through the Battle River—Crowfoot byelection in August 2025. Since then, every high-profile caucus departure has reopened questions about whether his leadership can keep MPs from different regional and ideological wings together. Brock’s move is not evidence of a revolt, but it arrives in a political environment where each exit inevitably attracts scrutiny.

Conservative Defections Helped Transform Carney’s Government

The four Conservative floor crossings mattered well beyond Conservative optics because they changed the arithmetic of Parliament. Carney’s Liberals emerged from the 2025 election with 169 seats, three short of the 172 seats required for a majority in the 343-seat House. Conservative defections by d’Entremont, Ma, Jeneroux and Gladu, along with NDP MP Lori Idlout’s move to the Liberals, steadily narrowed that gap while several Liberal-held seats were vacant.

The decisive step came in April 2026, when the Liberals won three federal byelections and reached 174 seats. Canadian Press described it as the first time in Canadian history that a federal government had moved from minority to majority status between general elections. That history explains why Conservative caucus movements now attract outsized attention. Brock is not strengthening the Liberal benches directly, but another Conservative vacancy creates one more contest in which the opposition must recruit a candidate, organize locally and defend territory while Carney governs from a much stronger parliamentary position than he held immediately after the 2025 vote.

Another Byelection Is Now on the Calendar

Once Brock’s resignation takes effect, federal law starts a defined byelection process. Elections Canada says a writ for a vacant House of Commons seat must generally be issued between the 11th and 180th day after the Chief Electoral Officer receives the Speaker’s warrant. The campaign itself must run within legally defined limits. Canadian Press reported that Brock’s September 18 departure means voters in Brantford—Brant South—Six Nations are expected to go to the polls by roughly mid-April 2027, provided a general election does not supersede the process.

The vacancy adds to an already crowded federal byelection calendar. Canadian Press reported that Brock’s seat will require another federal byelection as Parliament works through vacancies created by retirements, political moves and new appointments. The practical test for Poilievre is straightforward: nominate a credible local candidate, protect a seat Brock won by more than 11 percentage points in 2025, and prevent another departure story from turning into an electoral loss. For Carney’s Liberals, even making the race genuinely competitive would carry symbolic value in territory Conservatives have held federally since 2008.

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