He was previously mayor of Auburn Hills and a member of the Oakland County Commission.

McMillin graduated from the University of Michigan in 1987 with a bachelor's degree in economics and accounting.

In 2009, McMillin was of the most conservative politicians in Michigan, having defeated a Royal Oak gay rights ordinance and supporting a county commission resolution defining marriage as a union between a man and a woman.

[2] McMillin was the honorary chairman of Concerned Taxpayers of Michigan, a ballot question committee opposing a proposal to raise state taxes on the May 5, 2015 ballot.

[3] McMillin was elected chairman of the 8th Congressional District Republican Committee of Michigan on February 20, 2015.