The Ontario Liberal Party held a leadership contest in 2023 to elected a new leader to succeed former leader Steven Del Duca, who resigned after the party having failed to win enough seats to secure party status for the second time in a row in the 2022 Ontario general election. The leadership contest, featuring four candidates all having served in the House of Commons but only one with a current seat in the provincial legislature, concluded eighteen months later with balloting held on November 25 and 26, and resulted announced on December 2, 2023. Mississauga Mayor and former Liberal MP Bonnie Crombie was elected on the third ballot/count.

Background In the 2022 general election, the Ontario Liberal Party saw a modest increase in support over their 2018 result, finishing second in the popular vote. However, the party won only 8 seats, once again falling short of official party status. On the night of the election, Del Duca, who had failed to win back his own riding of Vaughan—Woodbridge, announced his resignation as party leader, stating that a leadership race would be organized to take place "as soon as is reasonable".

On January 5, 2023, the party released a report of their 2022 campaign debrief. One of the main recommendations was for the party to conduct a review of the leadership election process. On January 9, 2023, interim leader John Fraser announced that the party would proceed with consultations looking at whether there should be changes to delegated convention rules.

At it annual meeting held in Hamilton in March 2023, the party voted overwhelmingly to eliminate delegated leadership convention as the final step for leadership election and mandated that the next leader be elected by party members voting directly by ranked ballots. The new voting process and tabulation system retained the key basic premise that all electoral districts being given equal weight in the selection of the leader regardless of the size of their membership or their electoral history. The vote tabulation system adopted is substantially the same as the system used by the federal Liberal and Conservative parties, and the Ontario Progressive Conservative Party.

By voting to eliminate leadership convention, the Ontario Liberal Party made itself the bookends of a chapter of historical significance. Its 1919 leadership convention, held seven weeks before the federal Liberal convention that elected William Lyon Mackenzie King, was the first competitive leadership convention for any Canadian political party with parliamentary representation. Its 2020 leadership convention that elected Del Duca immediately before COVID lock-down was the last leadership convention held by any party of significance in Canada.

Rules and procedures Under the procedure outlined by the party's constitution and its rules of procedures, all members of the Ontario Liberal Party were eligible to vote directly for leader by preferential ballot and instant-runoff voting as long as they were members in good standing as of September 11, 2023. Except for members of a handful of sprawling northern and rural ridings, all member wishing to cast the ballot were required to do so in person with a paper ballot on November 25 and 26, 2023.

Upon the conclusion of the balloting, the ballot boxes were sealed and transported to the party headquarter in Toronto, and to the Metro Toronto Convention Centre for counting on December 2, 2023. The ballots cast in each Liberal riding association were counted separately, with each provincial electoral district being allocated 100 points, to be awarded to the leadership contestants in proportion to the number of first preference votes they received. Each of the party's ten recognized student clubs were allocated 50 points, and each of the party's recognized eight women's clubs were allocated 5 points.

Ballots were be counted on December 2, 2023. The first preference of all ballots were tallied in each count, with the candidate with the least weighted first preferences eliminated and their vote distributed base on second preference, and the process repeating until a candidate emerged with 50% of the vote. The counting process was smoother than most party officials and campaign operative have anticipated. The result was known in the counting room by mid-afternoon, well in advance of the time major networks had anticipated to carry their live coverage of the announcement.

Timeline June 2, 2022 – Ontario general election held, resulting in a second consecutive majority PC government. The Liberals won 8 seats, falling short of official party status. Party leader Steven Del Duca was again defeated in his home riding and announced his resignation from leadership in his concession speech. July 25, 2022 – John Fraser, who previously served as interim leader from 2018 until 2020, is unanimously selected by the Ontario Liberal caucus to serve as interim leader. August 3, 2022 – Party executive formally ratifies selection of Fraser as interim leader. March 3–5, 2023 – The Ontario Liberal Party held eights hours worth of constitution plenary at its annual meeting, during which it voted to eliminate delegated convention as the final step for leadership election and mandated that future leaders be elected directly by party members casting ranked ballots. It also adopted a vote tabulation system substantially similar to systems used by the federal Liberals and Conservatives, and the Ontario PC Party, retaining the key premise that all electoral districts associations having equal weight in leadership contests. It however diverged from the federal Liberals in continuing to grant significant weight to student liberal clubs in the leadership election. The annual meeting also saw the party's first hotly contested election for party president since 1999. Former Cambridge mayor and provincial transportation minister Kathryn McGarry emerged victorious. April 16, 2023 – OLP executive council announced timeline and fee schedule for the leadership contest May 8, 2023 – Nathaniel Erskine-Smith, federal MP for Beaches East York, announced his candidacy. May 28, 2023 – Ted Hsu, MPP for Kingston and the Island, announced his candidacy. A former federal MP, Hsu landed one of the Liberals' only two gains in the 2022 election, and was the only caucus members not elected from Ottawa or Toronto, June 3, 2023 – Yasir Naqvi, federal MP for Ottawa Centre and a senior minister in the Wynne ministry, announced his candidacy. June 14, 2023 – Bonnie Crombie, Mayor of Mississauga and a former Liberal MP, announced her candidacy. July 4, 2023 – Adil Shamji, MPP for Don Valley East first elected in 2022, announced his candidacy. July 8, 2023 – OLP President Kathryn McGarry releases detailed process information for the leadershio contest August 15, 2023 – Party announced the five debates and locations. September 5, 2023 – Candidate registration deadline. September 11, 2023 – Membership deadline to be eligible to vote in the leadership election as party member. The party initially estimated the total eligible voting members to be around 80,000. September 14, 2023 – First official leadership debate held in Thunder Bay. September 20, 2023 – Unofficial leadership debate held at Toronto Metropolitan University Democracy Forum, hosted by the Toronto Star. September 28, 2023 – Shamji dropped out of the leadership race and endorsed Crombie. October 1, 2023 – Second official leadership debate held in Stratford. October 24, 2023 – Third official leadership debate held at the Isabel Bader Theatre at the University of Toronto. October 26, 2023 – OLP announced that the membership review and duplicate removal process substantially completed with 103,206 members on the membership list. November 8, 2023 – Fourth official leadership debate held in Ottawa. November 9, 2023 – Yasir Naqvi and Nate Erskine-Smith held a joint press conference at Queen's Park announcing an agreement to each urge their supporters to select each other as their second preference. The pact also entailed cooperation of the two teams on volunteer deployment and get-out-the-vote efforts. November 15, 2023 – Leadership debate held on The Agenda with Steve Paikin, hosted by TVO, the first episode of The Agenda since the conclusion of the TVO Strike. November 19, 2023 – Fifth and last official leadership debate held in Brampton. November 25–26, 2023 – Ranked ballots cast in-person by party members. December 2, 2023 – Ballots counted, with the new leader announced the same day. December 2, 2023 – At 4:34 PM, Crombie was declared the new leader of the Ontario Liberal Party by party president Kathryn McGarry and MPP Stephen Blais.

Campaign

The party formally announced the start of the leadership election process on April 16, 2023, announcing the timeline, candidate registration requirements and fee schedule for the election.

There had been debate on the timing of the election, with campaigns that were actively exploring bids pushing for an earlier date in 2023, and others who wanted to delay the contest until late 2023 or early 2024, in the hopes of encouraging more candidates to join the race. In the end the party selected November 25–26 as the voting days with a new leader being announced on December 2, 2023.

Nate Erskine-Smith was the first to officially announce and register as a candidate, doing so on May 8, 2023. He was followed by Ted Hsu and Yasir Naqvi, who announced with a week of each other at the end of May/beginning of June, and who, like Erskine-Smith, had been actively organizing and campaigning in the preceding months.

Bonnie Crombie announced her candidacy on June 14, this was after announcing an exploratory committee in May and the Ford government announcing legislation to dissolve the Regional Municipality of Peel and make Mississauga a Single-tier municipality. The day after launching her campaign, Crombie was criticized for comments she made in regards to the greenbelt, suggesting that if she were premier she would be consider allowing land inside the greenbelt to be made open to development, although Crombie later clarified her position.

Adil Shamji announced his candidacy at the beginning of July.

In July, an interview featuring Nate Erskine-Smith appeared in the Toronto Star where he critiqued Bonnie Crombie's desire to move the party to the centre-right, her position on the Greenbelt and her age. In response to that interview, Crombie accused Erskine-Smith of sexism and ageism relating to his comments saying "we should be thinking of this as what party do we want to build for the next 15-20 years."

On August 15, the party announced the dates and locations for the five debates that are scheduled to be held across the province starting on September 14 in Thunder Bay.

On August 19, Adil Shamji expressed concerns about election interference after some of his social media accounts were disabled. Shamji's Twitter account was suspended over complaints of spam, then his Facebook account was disabled, preventing the campaign from advertising on the platform. Shamji called the complaints frivolous and malicious and suggested the potential that the suspensions were part of a coordinated attack attempt to silence or hinder his campaign.

On September 11, the party announced, following the deadline to join the party, that the total number of individuals who would be eligible to vote in the leadership election would be over 80,000. The party later announced that, following verification checks and the removal of duplicate submissions, that 103,206 members in total will be eligible to vote.

On September 28, Adil Shamji announced he will be dropping out of the leadership race to endorse Bonnie Crombie.