1990s Arnott first ran in the
1990 provincial election as the
Progressive Conservative (PC) candidate in the Riding of
Wellington at the age of 27; he was elected by a margin of 1,304 votes. At the time of his election, Arnott was the youngest MPP in the Ontario Progressive Conservative Caucus. Between 1990 and 1995, he served as PC Critic to the Minister of Transportation, and later as Critic to the Minister of Culture, Tourism, and Recreation, and as vice-chair of the Standing Committee on Estimates. In the
1995 provincial election, Arnott was re-elected in Wellington, receiving 67% of the votes cast, as part of a majority Progressive Conservative Government led by
Mike Harris. While supporting the overall objectives of the
Common Sense Revolution, the party's electoral platform, during the campaign he refused to sign the Taxpayers' Protection Pledge being circulated by the Ontario Taxpayers' Federation. Despite pressure from his party, he explained at the time that he was not willing to make promises that he could not be certain of keeping. He was the only member of the PC caucus not to sign the pledge. During the 1995–1999 term of office, he served as Chair of the Standing Committee on the Legislative Assembly, and later as Parliamentary Assistant to the Minister of Economic Development and Trade, with responsibilities for supporting small business. Re-elected in the
provincial election of 1999 in the newly created Riding of
Waterloo—Wellington, he served as Parliamentary Assistant to the Minister of Economic Development and later to the Minister of the Environment and then the Deputy Premier and Minister of Education. When
Ernie Eves was elected Premier in 2002, Arnott asked not to be considered for a Cabinet position, saying the absences from home required of a Cabinet Minister would not allow him to spend sufficient time with his young family.
2000s In the
2003 provincial election as
Dalton McGuinty's Liberals were given a majority, Arnott was re-elected in Waterloo-Wellington by a margin of 5,206 votes. This was despite a poll published by the Kitchener-Waterloo Record the week before the election predicting his defeat and claiming he was 18 percentage points behind his Liberal challenger. Returning again to the role of Opposition, Arnott was appointed by the Legislature as First Deputy Chair of the Committee of the Whole House, a Presiding Officer role assisting the Speaker of the House. In the
2007 provincial election, despite the re-election of a majority Liberal Government, Arnott was re-elected to the Legislature in the new Riding of
Wellington—Halton Hills, becoming a GTA MPP for the first time. He was again appointed First Deputy Chair of the Committee of the Whole House, serving in this role until 2009. After
Tim Hudak's election as PC Leader, Arnott became vice-chair of the Standing Committee on Public Accounts. Later his knowledge of House procedure was recognized with his appointment as Deputy House Leader of the Official Opposition.
2010s Arnott was again re-elected in the
2011 provincial election, which saw the McGuinty Liberals return with a minority Government. He was again appointed as First Deputy Chair of the Committee of the Whole House. After New Democratic Party Leader
Andrea Horwath announced her party would vote against the 2014 Liberal Budget, the new Liberal leader,
Kathleen Wynne, called a
provincial election for June 12, 2014. Even though the PC Party ran a poor campaign province-wide, Arnott was re-elected in Wellington-Halton Hills by a comfortable margin. Once again, he was appointed First Deputy Chair of the Committee of the Whole House. He was named PC Critic to the Minister of Economic Development, Employment, and Infrastructure, and also served as PC Critic to the Minister of Labour. In February 2017, he was named PC Critic to the Minister of the Environment and Climate Change. Over the years, he has introduced many
Private Member's Bills and Resolutions which have been passed by the Legislature or been adopted as Government Policy. A partial list of his legislative accomplishments includes his amendment to the Highway Traffic Act allowing volunteer firefighters to use a flashing green light on their personal vehicles when responding to an emergency. His resolution highlighting the Healthy Babies, Healthy Children program led to a 500 percent increase in its budget, allowing "at risk" children to be identified and receive the needed supports to reach their full potential. His amendment to the Workplace Safety and Insurance Board Act to allow municipalities to purchase the highest level of coverage for their volunteer firefighters was adopted as a Government bill and was passed into law. His resolution calling attention to the diminishing contribution by the Government of Canada to Ontario's health care costs was passed by the House, leading to a new health funding agreement. His controversial bill supporting "double hatter" firefighters received more hours of debate at 3rd Reading than any other Private Member's Bill in the history of the Legislature. Working with a Liberal MPP, he introduced the very first bill in the history of the Ontario Legislature co-sponsored by Members from different parties. That bill established August 1 as Emancipation Day in Ontario, recognizing the day when slavery was abolished in the British Empire in 1834, and was passed into law. Another amendment he proposed to the Workplace Safety and Insurance Board Act, to ensure volunteer firefighters were covered under "presumptive legislation" in the same manner as full-time firefighters, was adopted as Government policy. Another bill he introduced, co-sponsored by Liberal and NDP MPPs was passed recognizing January 21 as "Lincoln Alexander Day" in Ontario. Later a similar bill was passed by the Parliament of Canada. His resolution proposing a massive expansion of volunteer tree-planting efforts in Ontario for the province's 150th anniversary in Confederation was passed by the House, leading to the announcement of "Ontario's Green Leaf Challenge" program. In recent years, he has worked with local partners and advocated for infrastructure projects, including a new Groves Memorial Community Hospital, supporting renovations and improvements to the Georgetown Hospital, the Highway 6 Morriston bypass project, a new Wilfrid Laurier University campus in Halton, and a new Halton Courthouse. In November 2016, Arnott announced his intention to run in the 2018 provincial election. On June 7, 2018, he was re-elected to the Ontario Legislature representing Wellington-Halton Hills, receiving 31,659 votes or 54% of the ballots cast by voters. Across the province, the Progressive Conservative Party of Ontario won the election. On July 11, 2018, Arnott was elected as
Speaker of the Ontario Legislature on the first ballot. In the early months of the 42nd Provincial Parliament, Arnott struggled visibly in his new role. With a large number of newly elected MPPs routinely trading insults across the floor, his efforts to gain control of the raucous House were often drowned out by the noise. In July 2019, the Office of the Speaker released “Rules of Respect and Courtesy in the Chamber.” In it, Arnott urged MPPs to set a higher standard of behaviour in their day-to-day activities in the Legislature's Chamber. He continued to encourage MPPs to do better, and over time the debates in the House became more respectful and issue-focused, and somewhat less divisive.
2020s During the COVID-19 pandemic, Arnott was empowered by the House to implement safe entry protocols which applied to everyone entering the Assembly precinct. The protocols required people to present proof of being vaccinated against COVID-19, or proof of recent, negative rapid antigen test before being admitted to the House. On December 7, 2021, Independent Cambridge MPP Belinda Karahalios was ejected from the Legislature, having refused to divulge her vaccine status to the Legislature's staff, but seeking entry to the House by presenting a negative rapid antigen test. Because she had recently tested positive for COVID-19, Arnott declared the test result to be unreliable, citing current public health advice, and expelled her from the House. On September 26, 2020, Arnott was nominated as the Ontario Progressive Conservative Party's candidate in Wellington-Halton Hills for the
2022 provincial election. He was re-elected to the Assembly for a ninth term. On August 8, 2022, he was re-elected Speaker for the 43rd Provincial Parliament. On April 17, 2024, in response to the
situation in Palestine and Israel, Arnott prohibited
Palestinian kaffiyehs from being worn by anyone —
MPPs or guests — in the Ontario legislature over concerns the scarves make “an overt political statement." Ontario Premier Doug Ford immediately urged a reversal of Arnott's ban. ==Honours and recognition==