Controversially, her government introduced a reformed sex education curriculum, brought in a cap-and-trade pollution pricing regime with Quebec and California, and privatized Hydro One.

In 1996, she helped found Citizens for Local Democracy, which opposed the amalgamation of Metropolitan Toronto undertaken by the Progressive Conservative (PC) government of Premier Mike Harris.

In 2001, Wynne helped pass a measure encouraging public schools to purchase teaching materials reflecting the presence of gay and lesbian parents in modern society.

[23] The Liberals won the election, and Wynne was appointed parliamentary assistant to Minister of Training, Colleges and Universities Mary Anne Chambers, in October 2003.

[34] Days before members were to begin electing delegates Glen Murray announced he was exiting the leadership race and endorsed Wynne's candidacy.

[36] Pupatello was also believed to have the most support among ex officio delegates, which are MPPs, MPs (members of parliament), defeated candidates and other Liberal insiders, and was expected to increase her lead over Wynne on the first ballot at the convention.

[37][38] At the convention on January 26, 2013, she used her speech to discuss repairing relations with teachers and working with opposition parties, and took aim at her main rival Pupatello, who did not hold a seat, by saying that she was ready to govern and would recall the legislature on February 19.

Wynne also addressed her sexuality saying; "When I ran in 2003, I was told that the people of North Toronto and Thorncliffe Park were not ready to elect a gay woman.

[45][46] Opposition parties accused Wynne of having a role in the McGuinty government's costly decision to cancel the construction of gas plants in Mississauga and North-East Oakville in 2011, when she was co-chair of the Liberal campaign.

[51][52] In February 2013, the legislative committee that had been investigating the gas plants cancellation prior to McGuinty's resignation and prorogation of the legislature in October resumed its work.

[54] In June 2013, opposition parties called on the Ontario Provincial Police (OPP) to open an investigation into new allegations that staffers in Premier McGuinty's office had deleted emails regarding the gas plants.

Among other things, the act required all MPPs, cabinet ministers, parliamentary assistants, opposition leaders, and their respective staff to post their expense reports online, expanded the powers of the integrity commissioner and ombudsman, and introduced a fine of $5,000 for the willful destruction of government records.

[58][59] In April 2014, Wynne launched a libel lawsuit against PC MPP Lisa MacLeod and Party Leader Hudak after they said that she "oversaw and possibly ordered the criminal destruction of [gas plant] documents".

[61] In 2016, Kathleen Wynne decided to sell 30 per cent of Hydro One, an electric utility Crown corporation, to private owners.

[69] Kathleen Wynne's involvement with the administration of grade school and post-secondary education was largely marked by labour disruptions and teacher strikes.

Wynne immediately started new collective bargaining negotiations with the Elementary Teachers Federation of Ontario (ETFO) after a year of labour distress that had culminated in the Putting Students First Act, 2012,[70] which had suspended collective bargaining rights, imposed contracts on teachers and suspended the right to strike.

The first public poll of the campaign, conducted by Forum Research, showed the PCs ahead in the popular vote, but the Liberals likely on track to retain a minority government.

[94] Wynne ran a fairly controversy-free campaign, although her performance in the televised leaders' debate on June 3 was criticized by pundits as being weak and she was on the defensive for many of the scandals that had plagued her predecessor, Dalton McGuinty.

She began to eat away at the NDP's traditional left-wing support, especially in and around Toronto, and the controversies over some of Hudak's economic policies hurt him among centrist voters across the province.

Furthermore, Wynne ran hard near the end of the campaign on the premise that in a close election, the Liberals were the only party who were in a position to defeat the PCs.

There was also controversy surrounding a cartoon in the Sun newspapers during the final week of the campaign that showed a pair of broken glasses, presumably Wynne's, smashed on the ground with a smattering of blood.

One pollster, Ipsos Reid, still projected on the final day of the campaign that the PCs were ahead among likely voters, and that the NDP and Liberals were tied at around 30 per cent.

On election day, Wynne's Liberals led province-wide all night as they captured a fourth term in office, and moved from minority to majority government.

[98] On July 2, Wynne re-convened the Ontario Legislature to pass the budget that had been introduced, but not voted on, prior to the writs being dropped for the election.

Kathleen Wynne, under the advice of Ed Clark, partially privatized Hydro One and reformed the Alcohol and Gaming Commission of Ontario's Liquor Licence Act to allow the sale of six-packs of beer in Ontario grocery stores, the latter of which was the result of a Toronto Star exclusive on the anti-competitive practices made by the privately owned Beer Store.

[102] In education, the provincial government announced it would provide free college and university tuition for students from families with an annual household income of less than $50,000.

During this session, Wildrose Party MLA (Member of the Legislative Assembly) and finance critic Derek Fildebrandt attacked her economic policies by calling Ontario a "fiscal basket case".

[111] Fildebrandt was expelled from the Wildrose caucus, but was later re-admitted, after he apologized and claimed that his support of the homophobic comment on Facebook had been "an honest mistake".

[116] In March 2017, the Liberal government announced "free tuition" for families earning less than $50,000 by updating the Ontario Student Assistance Program (OSAP).

[119] Wynne's Liberals headed into the 2018 provincial election campaign trailing far behind the PCs, led by former Toronto City Councillor Doug Ford.