Elected to
Gunnedah Shire Council in 2004, aged 19, Marshall became deputy mayor and then
mayor of Gunnedah, an office his father once held, after the 2008 local government elections. During his time as Mayor, Marshall served as president of the Country Mayors' Association and Senior Vice-President of the Shires Association of NSW. Marshall moved to
Armidale in 2012, resigning from the council, and commenced studying
commerce at the
University of New England, prior to his endorsement as a candidate for the March 2013 by-election held after sitting independent member
Richard Torbay was forced out of politics amid allegations of corruption. Marshall would claim victory on election night having receiving over 60% of the vote, subsequently being declared the winner with a margin of more than 30%. This was not considered an upset; in 2011, the Nationals would have won it with a majority of 26.1 percent in a "traditional" matchup with
Country Labor. Marshall won a full term almost as easily in
2015, boosting his majority to 27.1 percent, the third-safest in the state. He was reelected in
2019, and now sits on a majority of 33.8 percent, the safest in the state. During his preselection bid ahead of the Northern Tablelands by-election in 2013, it was revealed that Marshall once held concurrent membership with both the Nationals and Labor from 2001 to 2003, while also being employed on the staff of
independent Member for Tamworth,
Peter Draper. Country Labor organiser
Courtney Roche said Marshall would have been deemed to be a card carrying member of the party until 2004, after which his membership expired. Having served on several standing, select and statutory Parliamentary Committees, as well as in the position of Temporary Speaker, Marshall was appointed to the position of Parliamentary Secretary for Northern New South Wales and Renewable Energy on 25 August 2016. Following the resignation of
Mike Baird as Premier,
Gladys Berejiklian was elected as
Liberal leader and sworn in as Premier. The
first Berejiklian ministry was subsequently formed with Marshall sworn in as the Minister for Tourism and Major Events, and Assistant Minister for Skills with effect from 30 January 2017. ==Personal life==