 On April 25, 2018, physician Mark Freeman announced a primary challenge to Mast, focusing on his promise to "defend the Second Amendment" and be an "unwavering partner" to President Trump.Freeman called Mast an "establishment candidate" and complained about Mast's shift on gun control issues after the Parkland school shooting.Mast defeated Freeman in the Republican primary and moved onto a general election battle against Democratic nominee Lauren Baer, an attorney and foreign policy expert who served as an official in the Obama Administration.