Formerly a Progressive Conservative MLA in the Legislative Assembly of Manitoba, he was elected to the House of Commons of Canada in a by-election on November 25, 2013.

He was named mid-Canada's Outstanding Young Farmer in 1986, and received a Certificate of Merit from the Manitoba Agricultural and Food Sciences Grads Association in 1990.

[2] He was also chairman of the Agricultural Diversification Alliance (ADA) and a public governor of the Winnipeg Commodity Exchange in this period, and advocated changes to the federal Crow Equity Fund.

[8] In June 1993, Maguire upset provincial cabinet minister Jim McCrae to win the Progressive Conservative Party of Canada nomination for Brandon—Souris in the 1993 federal election.

Maguire emphasized farming issues in his nomination speech, and argued that he would be successful in bringing Reform Party supporters back to the Progressive Conservatives.

In the lead up to the 2019 election, Maguire was one of 27 candidates with a strong environmental track record from across the political spectrum to be endorsed by GreenPAC.

This includes securing funding for water management and wetland restoration projects such as the Assiniboine River Basin Initiative.

[12] Maguire sought the Progressive Conservative Party of Manitoba nomination for Arthur-Virden in April 1999, but lost to rival candidate Gary Nestibo.

[14] Maguire finished second on the first ballot, behind Gary's wife Lorna Nestibo, but won on the second count with support from third-place candidate Grant Fotheringham.

Maguire was appointed as the Progressive Conservative critic for the environment, and lobbied for improvements to the provincial Water Rights Act.

[24] In 2002, he was one of five PC MLAs to support a government motion granting pension, alimony and death benefits to gay and lesbian spouses.

In September 2007, he was replaced as deputy leader by Myrna Driedger[29] and was appointed Critic for Infrastructure and Transportation, Government Services, and Competitiveness, Training and Trade.