I like to imagine that this revelation came to her in the course of her day, as a vague, nagging worry that there was something she was supposed to do. “Did I … leave the stove on? No, no. I remember turning it off. Did I … maybe forget my keys? Nope, got ’em right here. What was it? It was something to do with … the air. Replace the air filters, maybe? Noooo… WAIT. THE PLANE.”

Look on the bright side, though. Now she’s qualified to be Treasury Secretary.

McCaskill has been answering questions about the plane since POLITICO recently reported that she billed taxpayers for a political trip around Missouri. POLITICO also reported that McCaskill spent $76,000 from her Senate budget on trips on the aircraft over the past four years, prompting the senator to refund the Treasury Department more than $88,000 for the cost of the trips plus pilot fees. McCaskill’s announcement Monday is the latest twist in a political scandal that has dogged her for the past two weeks. The expensive fiasco clashes with her self-made image as a reformer and good-government advocate during her first term in the Senate. McCaskill has now shelled out more than $375,000 in payments to cover the cost the plane flights and back taxes, a series of events the senator herself has called “embarrassing.” On top of this, McCaskill signed on in February as a co-sponsor of Senate legislation that would fire federal employees if they are “seriously delinquent” in paying their own federal taxes… “There are people I could blame for this, but I know better. As an auditor, I know I should have checked for myself. I take full responsibility for the mistake,” added McCaskill, Missouri’s former state auditor from 1999 to 2007. “I should have checked the documentation. I should have been asking the questions. I shouldn’t have assumed that somebody was doing it.”

The tax she didn’t pay was a state personal property charge on aircraft hangared in Missouri. To end her problem once and for all, she says she’s now convinced her husband to “sell the damn plane,” which I guess means commercial flight and possible TSA grope-downs henceforth. Congratulations, Claire: You really are one of the people now.

That boldface part in the blockquote is going to make a dynamite attack ad during the campaign next year, needless to say. As for now, via Mark Hemingway, here’s what the NRSC has cooking.