The seat leans slightly Republican, giving Mitt Romney 51 percent of its vote in 2012, and is the type Democrats need to win to have a shot at taking back control of the House next year.
Walberg first won his seat in 2006 by defeating another Republican congressman in a campaign helped by big spending from the conservative Club for Growth. He lost his seat in the 2008 Democratic wave in a tight race with Rep. Mark Schauer (D-Mich.), then defeated Schauer during the 2010 GOP wave before winning by a double-digit margin in 2012.
Byrnes served three terms in Michigan's statehouse before losing a Democratic primary for a state senate seat in 2010. She has a centrist reputation and was one of the few Democrats to back a plan to change teacher pensions in the state, which may have cost her labor support in that race.