After graduating from law school at Western Michigan University, Hagerstrom began working as a legislative aide in the Michigan House of Representatives in 1997. Beginning in June 2008, Hagerstrom served as the Michigan state director for the state chapter of Americans for Prosperity, a political nonprofit organization associated with Charles and David Koch. Hagerstrom left AFP in early February 2015. In February 2015, Hagerstrom joined the Coalition Against Higher Taxes and Special Interest Deals, a group formed by Paul Mithcell to oppose Michigan Proposal 1. Hagerstrom was hired as the group's director of grassroots and strategic engagement. Proposal 1 was on the May 5, 2015 ballot in Michigan as a legislatively referred constitutional amendment, where it was defeated. Hagerstrom joined the Trump campaign in December 2015. He was a district-level delegate to the 2016 Republican National Convention.