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Democratic U.S. Sen. Amy Klobuchar raised $1 million during the first three months of 2012, adding to her already robust reelection campaign reserves. With the latest preliminary fundraising numbers released by her office Friday, Klobuchar has almost $5.2 million in the bank as she seeks her second Senate term.

None of the Republican candidates seeking to unseat Klobuchar have formally filed campaign paperwork with the Federal Election Commission, but Minnesota Army National Guard Capt. Pete Hegseth's campaign reports that he raised $160,000 during his first month in the race and has $130,000 of that in the bank.

Former state Rep. Dan "Doc" Severson and freshman state Rep. Kurt Bills, who recently entered the race, are expected to file their fundraising totals this weekend. Severson had raised about $34,150 by the end of 2011, records show.

The totals released Friday won't include proceeds from a Wednesday fundraiser in Minneapolis featuring U.S. Vice President Joe Biden. Ticket costs for that event ranged from $10,000 to $125. During the event, Biden called Klobuchar a close ally of the Obama administration.

Though her fundraising totals dwarf those of her potential opponents, Klobuchar told supporters their contributions would help counter the millions of dollars that national Republican-backed super political action committees may spend in an effort to defeat her.