Mason first ran for Edmontoncity council after he was temporarily laid off from ETS in 1983, before becoming president of the Edmonton Voters Association, a municipal political party. He tried again for a seat on the council in 1989 with a dynamic campaign running in Ward 3. Mason's campaign came with a legal challenge he mounted against a provincial law forbidding municipal employees from running as candidates in a civic election unless they resigned their position with the city. The legal challenge was unsuccessful, however Mason was elected city councillor for Ward 3 in October 1989. Shortly after the election the law Mason challenged was repealed, and municipal workers in Edmonton were subsequently allowed to run for civic office without resigning their positions. Mason remained on city council until 2000, when he ran for political office for the New Democratic Party.
Provincial politics
In 2000, following the mid-term resignation of then leader of the Alberta New Democrats and MLA for Edmonton Highlands Pam Barrett, Mason left city council and ran for the NDP in the ensuing by-election. He held the Legislative Assembly seat with a strong majority, and was re-elected in the 2001 provincial election.
Alberta NDP Leader
Mason was appointed the role of interim party leader for the NDP following the resignation of then leader Raj Pannu in July 2004. He became the official leader of Alberta's NDP on September 18, 2004, following a vote at the party convention. Mason held his seat during the provincial election in 2004, which saw the caucus welcome the return of former leaders Pannu and Ray Martin, along with newcomer David Eggen. In the provincial election of 2008 Mason again retained his seat, and was joined in caucus by newly elected NDP MLA Rachel Notley from Edmonton-Strathcona, the seat previously held by Pannu. During his tenure as a Member of the Legislative Assembly, Mason has become the outspoken champion of issues such as:
Mason also hosted various community meetings across the province. In 2009, Mason hosted a Round Table forum to discuss provincial budget concerns with a wide cross-section of Albertans. In 2009 and 2010, Mason hosted two provincial tours, each visiting several Alberta communities. The first tour took place in September 2009, with the public forums focusing on health care concerns, and resulted in the publication of the What People Want report. This report included more than 35 recommendations for health care reforms that would protect public services and improve the general health of Albertans. The second tour took place in May 2010, where the NDP again held public consultations. This time they invited Albertans to discuss concerns over the future of Alberta's energy economy and environment, as well as the erosion of public health services including long-term care. In the 2012 provincial election the NDP picked up two seats in Edmonton, regaining their previous four seat total. Both Notley and Mason safely held onto their seats while David Eggen was re-elected as the member for Edmonton-Calder. Newcomer Deron Bilous was also elected in Edmonton-Beverly-Clareview, the seat formerly held by Martin. In many other ridings the party also won more votes than it had attained previously. On April 29, 2014, Brian Mason announced that he would step down as leader as soon as a leadership election could be held to choose his successor. Mason who had mentored Rachel Notley convinced her to run for the leadership which she won. During the final few months of Mason's tenure the party was already enjoying strong polling in Edmonton, something which would eventually grow into the larger electoral sweep that the Alberta NDP managed in the 2015 provincial election under Mason's successor Notley that resulted in the formation of Alberta's first ever NDP government.
