Klobuchar gets stronger challenger in Minnesota

"I'm tired of Washington liberals bringing their ideas to Minnesota," Hegseth said in his announcement video. "It's time for us to bring our Minnesota ideas to Washington."

Klobuchar remains the odds-on favorite to retain her seat. She has some of the highest approval ratings of any senator in the country: Sixty-one percent of Minnesotans approve of the job she's doing while 28 percent disapprove, according to a recent poll by Democratic-affiliated Public Policy Polling. She also had $4.5 million cash on hand as of the end of 2011.

But Hegseth could make her work harder than the other candidates in the race. He has a national fundraising network from his time running Vets for Freedom, a hawkish foreign policy advocacy group, and, as his announcement video shows, is a fairly polished public speaker.

His status as a veteran could also help. He has a bronze star from his service in Iraq and just returned from Afghanistan in February.

Some state Republicans had hoped after former Gov. Tim Pawlenty (R) dropped his presidential  that he would run, but he declined and they'd been left without a serious challenger to Klobuchar. None of her other opponents had shown any life in fundraising numbers or on the campaign trail.