The lone Republican-controlled congressional seat in Maryland will be contested this fall.
Mia Mason, a registered Democrat who served in the U.S. military for more than 15 years, is running for the 1st Congressional District seat, which has been held by Andy Harris, a Republican, since 2011.
In a brief interview Thursday, Mason, who is transgender, pointed to Harris' voting record on LGBT rights and health care as one reason she was running.
"His voting record is what struck me, against our women’s veterans, our LGBT groups and him not representing our district properly for the needs and the services we need," Mason said.
Harris also faces a primary challenge by Jorge Delgado, and Mason will run against Harford County Democrat Erik Lane, a farm owner and tech entrepreneur.