Emmer, who came within one percentage point of defeating now-Minnesota Gov. Mark Dayton (D) three years ago, announced his bid for the conservative-leaning seat Wednesday evening.

"It seems like every day, we hear about another out-of-control Washington, D.C., power grab," Emmer said in a speech announcing his bid in his hometown of Delano, Minn., promising to bring "the spirit of Main Street to Washington."

He's known for his strongly conservative views — including a call during his gubernatorial campaign for a state law that all federal laws must be approved before being implemented in Minnesota. He's likely to face a crowded GOP field in the Republican-leaning district.

While none of the GOP candidates have Bachmann's star power, the controversial congresswoman's decision to retire rather than face a tough reelection battle makes her party's chances of holding the seat much better. Businessman Jim Graves (D), who nearly beat Bachmann in 2012 and had already announced another bid against her, dropped out of the race shortly after she did, depriving Democrats of a top-tier recruit in the state's most conservative district.