Sen. Claire McCaskill, a Missouri Democrat, was expected to have a difficult 2012 re-election campaign according to the political experts who handicap such things.

University of Virginia political scientist Larry Sabato has her listed as “very vulnerable.”

So the last thing she could afford was to have a story erupt that will give her Republican opponent ready made negative campaign ads, assuming she doesn’t have a primary challenge or survives same.

Unfortunately for her, that has happened. Politico broke the story earlier this month about McCaskill billing the government for the use of a plane she co-owns with her husband.

White there were no indications of illegality or ethics violations in terms of the flights and McCaskill has said she’d repay more than $88,000 to the U.S. Treasury, a realization of how toxic the story is in the current political climate.

But on Monday the story got even more poisonous for her political future. Politico reported that she and her husband failed to pay $287,273 in personal property taxes on the airplane.

McCaskill is known for being a frequent Twitter user but it doesn’t appear she’s tweeted on this yet.

And that’s despite obviously having some passionate feelings about the aircraft. A Politico excerpt:

“I have convinced my husband to sell the damn plane,” McCaskill said on a conference call with reporters. “I will never set foot on the plane again.”