After the riding switched back to the Liberals following the 1995 election, Stewart joined the new Saskatchewan Party which had essentially replaced the scandal-ridden PC's as the largest centre-right party in the province. This time, he defeated Swenson for the nomination. Stewart then unseated incumbent Liberal Gerard Aldridge in the 1999 general election. Stewart represented the constituency of Thunder Creek until its abolition in 2016.[4] Stewart was subsequently elected in Lumsden-Morse, a new electoral district encompassing most of the former Thunder Creek constituency.
Stewart had been the Minister of Agriculture and the Minister Responsible for Saskatchewan Crop Insurance Corporation since May 25, 2012, a role he maintained following the August 23, 2016 cabinet shuffle.[5] He had been a member of the Executive Council of Saskatchewan since the Saskatchewan Party won its first majority government in 2007, previously serving as the Minister for Enterprise and Innovation.[4] On August 9, 2018, he announced he was resigning from Cabinet due to health concerns.[6] In late 2020 Stewart was named Legislative Secretary to the Premier responsible for Provincial Autonomy and also the role of Provincial secretary.[7]
Stewart caused controversy in October 2022 when his mentor Colin Thatcher attended the Speech from the Throne. Thatcher was on parole for the murder of his wife, JoAnn Wilson.[8] Stewart later acknowledged in a statement that he had invited Thatcher, whom he called a "friend", and admitted that the invitation was an "error in judgment". He was removed from his role as legislative secretary by Saskatchewan Premier Scott Moe but permitted to remain as a party caucus member.[9]
On March 6, 2023, Stewart announced his resignation from the legislative assembly effective March 10, citing health reasons.[10]
