In 1994, he was elected as a city councillor for the suburban municipality of Scarborough. In the elections of 1997 and 2000, he was elected as a councillor in the amalgamated "megacity" of Toronto. During his time in municipal government, Duguid was known for his work on community safety issues and affordable housing. He drafted a crime-prevention strategy for Toronto in 1999, and was a founder of the "Scarborough Community Safety Council", the "Scarborough Community Safety Audit Program" and the "Business Crime Prevention Seminar Program". He was also known as a supporter of then-Mayor of Toronto, Mel Lastman. In the 2003 election, Duguid supported John Tory over David Miller for Mayor of Toronto.
Provincial
On May 1, 2003, Duguid was appointed by Liberal leader Dalton McGuinty as the party's candidate for Scarborough Centre in the upcoming provincial election. This upset many in the local party association, as 1999 Ontario general election candidate Costas Manios was widely expected to win the nomination again. Manios decided to run against Duguid as an Independent, and many believed he would deny Duguid victory by splitting the Liberal vote. Instead, the provincial trend overrode local factors—Duguid defeated incumbent Progressive ConservativeMarilyn Mushinski by over 10,000 votes, while Manios finished fourth, behind Michael Laxer of the Ontario New Democratic Party. On October 23, 2003, Duguid was appointed Parliamentary Assistant on urban issues to John Gerretsen, the Ontario Minister of Municipal Affairs and Housing. As such, he has often clashed with Mayor David Miller over allegations by the mayor that the province has reneged on funding promises to the city. Following his re-election in 2007, Duguid was appointed Minister of Labour. He ensured job protection for military reservists and improved health and safety in the workplace. He also saw the creation of the new Family Day holiday, allowing Ontario families to spend quality time together. In a Cabinet shuffle on September 18, 2008, Duguid was appointed as the province's Minister of Aboriginal Affairs. As Minister of Aboriginal Affairs from 2008 to 2010, Duguid worked at building relationships through agreements with a number of First Nations and Métis organizations, including the framework to transfer Ipperwash Park to the Kettle and Stoney Point First Nation. Uniting two of his passions – youth outreach and hockey – Duguid also brought PLAY to First Nations' youth, a project that provides hockey coaching, mentoring and, potentially, facilities to Aboriginal communities in the north. On January 18, 2010 he was appointed Minister of Energy and Infrastructure. In the re-election and subsequent Cabinet shuffle, in October 2011, the Cabinet was dissolved, and the Ministry of Energy and Infrastructure was split into two Ministries. The resulting cabinet Duguid was appointed as the Minister of Energy. In the Cabinet, post election, on October 20, 2011, Brad Duguid was appointed Minister of Economic Development and Innovation. In December 2012, CTV London reported that some of Minister Duguid's Christmas cards were sent without postage, instead using franking stickers only available to the monarch, federal MPs, senators and certain parliamentary employees. A staffer later resigned over the controversy. After Kathleen Wynne took over in 2013, she appointed Duguid as the Minister of Training, Colleges and Universities. Duguid was re-elected in the June 2014 election. After the election he was appointed as the Minister of Economic Development, Employment and Infrastructure. On June 13, 2016, Duguid's portfolio was changed to Minister of Economic Development and Growth. In September 2017, Duguid announced he would not be running for re-election in the next 2018 Ontario general election. His constituency was won by the Progressive Conservative candidate, Christina Mitas.
