Claire Mccaskill

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Democratic Sen. Claire McCaskill walks off the stage with challengers Republican W. Todd Akin (left) and Libertarian Jonathan Dine after their debate in the Missouri Senate race in Columbia, Mo., on Sept. 21. (Associated Press)

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Democratic Sen. Claire McCaskill (right) speaks Sept. 21, 2012, as she looks toward Republican challenger Rep. Todd Akin during the first debate in the Missouri Senate race in Columbia, Mo. (Associated Press)

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Sen. Claire McCaskill, Missouri Democrat, speaks during a meeting of the St. Louis Regional Chamber and Growth Association Sept. 7, 2012, in St. Louis. McCaskill is running for re-election against Republican challenger, Rep. Todd Akin. (Associated Press)

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"We have rules about tax credits and benefits, and it seems to me they need to be applied fairly and across the board," said Sen. Claire McCaskill, Missouri Democrat. "If there are rules, they need to be enforced. I think it's just that simple. I don't think it's complicated." (Associated Press)

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Sen. Claire McCaskill, Missouri Democrat, who won her seat narrowly in 2006 and is up for re-election in 2012, has no shortage of would-be GOP challengers. (Associated Press)

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Sen. Claire McCaskill and her husband agreed Monday to pay more than $287,000 in overdue property taxes on a private airplane she used for official business. She had used the aircraft for a political trip. "Millionaire Claire McCaskill wants to simply write yet another big check and hope people won't ask any more questions," said Republican Party official Rob Jesmer. (Associated Press)