John Howe, a former Republican state senator and one-time mayor of Red Wing, said Tuesday he is running for the open seat in Congressional District 2.

U.S. Rep. John Kline's retirement left an opening in the southeastern Minnesota congressional district. Kline is a Republican, but CD2 is seen by both parties as a swing district. 

Howe was elected to the state Senate in 2010 but lost re-election to a Democrat in 2012. He previously served two years as mayor of Red Wing. He also lost a GOP endorsement bid for secretary of state in 2014. 

Howe, a businessman and property owner, said he was planning to spend $300,000 to $500,000 of his own money on the race. "I think it'll take between $3 million and $4 million to win this race, but if you're going to ask others to invest in you, you have to show you're willing to invest in yourself," he said. 

David Gerson is also running on the Republican side. State Rep. Tony Albright of Prior Lake and former state Sen. Ted Daley of Eagan are considering it. Howe said he would seek the GOP endorsement but is undecided whether he'd run in the primary without it. 

Angie Craig, a business executive, and Mary Lawrence, a doctor, are both running on the DFL side.