McCallum contested the selection for the National Party candidacy for the
2015 Northland by-election, but lost to Mark Osborne. McCallum was the campaign chairman for MP
Matt King in the 2020 general election, when King lost his seat. After joining the
2022 protests at Parliament, King resigned from the National Party. McCallum was selected by the
National Party to contest the electorate at the . He was 68th on the
party list. On election night McCallum received more than 16,272 votes, beating incumbent
Willow-Jean Prime by a margin of 6,087 votes. ==Views and positions==