He received a triple Bachelor of Arts in economics and political science/history in 1989 from Concordia College and attended Georgetown University Law School, earning a J.D.

Johnson then practiced at the law firms of Lord, Bissell and Brook in Chicago and Parsinen, Kaplan & Levy in Minneapolis.

In 2000, Johnson successfully ran for the Minnesota House of Representatives in District 34B, winning 62.8 percent of the vote for the seat vacated by Henry Todd Van Dellen, who had retired.

[6] In 2011, Johnson ran against Tom Emmer for the position of Minnesota's Republican National Committeeman, winning an upset victory.

On August 14, in what many political commentators considered an upset, Johnson defeated former governor Tim Pawlenty in the primary election to become the party's nominee.

In March 2010, the Hennepin County Board tabled a request by Sheriff Rich Stanek to spend $426,150 to acquire the cellphone spying program KingFish.