The party adopted a position in favour of uniting Britain's North American colonies, a concept that led to Canadian Confederation.

Later, he battled with the federal Liberal Party of Canada government of William Lyon Mackenzie King, which, Hepburn argued, was insufficiently supportive of the war effort.

[14] Throughout the 1960s and 1970s, the Liberals were almost shut out of Metropolitan Toronto and other urban areas and, in 1975, fell to third place behind the Ontario New Democratic Party (NDP) under Stephen Lewis.

The Liberals remained more popular than the Tories among Catholic and Francophone voters, due to the party's support for extending separate school funding to include Grades 11–13.

Peterson modernized the party and made it appealing to urban voters and immigrants who had previously supported the cautious government of Tory Premiers John Robarts and William Davis.

On the campaign trail, the media reported that the Liberals were met by voters who were angry at going to the polls just three years into the government's mandate.

Another negative factor was Peterson's association with Mulroney and the failed Meech Lake Accord attempt at constitutional reform, about which the public felt strongly.

The party had also underestimated the impact of the Patti Starr fundraising scandal, as well as allegations surrounding the Liberal government's links with land developers.

The NDP promised a return to the activist form of government that had prevailed from 1985 to 1987, and its co-operation with the Liberals during that time made it appear more moderate and acceptable to swing voters in the Toronto area.

The Liberal Party was expected to replace the unpopular NDP, but it ran a poor campaign under leader Lyn McLeod, and was beaten by the Progressive Conservatives under Mike Harris.

Starting in fourth place, McGuinty's fiscally prudent record and moderate demeanor made him the second choice of a convention polarized around the candidacy of former Toronto Food Bank head Gerard Kennedy.

In the 1999 election, the governing Conservatives were reelected on the basis of strong economic growth and a negative campaign tightly focused on portraying McGuinty as "not up to the job".

With the Liberals consolidated as the primary opposition to Harris's Progressive Conservatives, McGuinty was able to present his party as the "government in waiting".

He personally rebuilt the party's platform to one that emphasized lowering class sizes, hiring more nurses, increasing environmental protections and "holding the line" on taxes in the buildup to the 2003 election.

McGuinty also made a serious effort to improve his debating skills, and received coaching from Democratic Party trainers in the United States.

[19] The new government called the Legislature back in session in late 2003, and passed a series of bills relating to its election promises.

The government brought in auto insurance reforms (including a price cap), fixed election dates, rolled-back a series of corporate and personal tax cuts which had been scheduled for 2004, passed legislation which enshrined publicly funded Medicare into provincial law, hired more meat and water inspectors, opened up the provincially owned electricity companies to Freedom of Information laws and enacted a ban on partisan government advertising.

It was revealed that a number of key figures associated with Mike Harris's "Common Sense Revolution" had received lucrative, untendered multimillion-dollar consulting contracts from these institutions.

This violated a key Liberal campaign pledge not to raise taxes, and gave the government an early reputation for breaking promises.

The Liberals defended the premium by pointing to the previous government's hidden deficit of $5.6 billion,[20] and McGuinty claimed he needed to break his campaign pledge on taxation to fulfill his promises on other fronts.

Soon after the federal election, McGuinty hosted a federal-provincial summit on public health-care funding which resulted in a new agreement for a national health accord.

During early 2005, McGuinty called the Legislature back for a rare winter session to debate and pass several high-profile bills.

The size of Prince Edward Island, the Greenbelt protects a broad swath of land from development and preserves forests and farmland.

[21] In the next general election on October 6, 2011, McGuinty led the Liberals to win a historic third consecutive term and to once again form government, albeit with a minority of seats in the legislature.

[26][27] The government pivoted to the left in the lead up to the 2018 election by raising the minimum wage, introducing reforms to employment standards and labour law, bringing in a limited form of pharmacare and promising universal child care.

In the 2018 general election, the Liberals were swept from power in a historic defeat that resulted in large gains for both the Progressive Conservatives and NDP.

The seven-member rump caucus was one short of the requirement to retain official status in the Ontario legislature, and was also the only remnant of Wynne's cabinet.

[29] In March 2020, the party elected former Cabinet Minister Steven Del Duca as leader, who defeated five other candidates on the first ballot at the leadership convention.

[37] Past presidents of the party include Yasir Naqvi, Joe Cruden, Jeffrey King[38] and Pat Reid.

[40] 1The Liberals were recognized as the Official Opposition following the 1923 election by the governing Conservatives, despite the fact that the United Farmers of Ontario had more seats.