Gruenhagen is a resident of Walcott, Iowa, and became a member of the Muscatine County branch of the Farm Bureau in 1994.

[1] Gruenhagen announced his intention to run for District 41 of the Iowa Senate in December 2021.

[2] The seat was open following redistricting, as Jim Lykam retired and Roby Smith opted to run for state treasurer.

[1] Gruenhagen defeated Alan Weets in the Republican Party primary election, held in June 2022.

[3][4] Gruenhagen won the November 2022 general election against Democratic candidate Deb VanderGaast.