Sen. Claire McCaskill (D-Mo.) missed the deadline to pay her property taxes on her Washington condo by three weeks, incurring a nominal penalty for filing late.

McCaskill paid a $197 penalty plus interest on the $1,514 she owed for a six-month period, the Kansas City Star reported. McCaskill was also late paying the bill in 2010 and 2008.

"Unlike other jurisdictions that bill just once a year, they bill twice a year," McCaskill told the paper. "Somehow the second bill that came to my condo in D.C. slipped through the cracks, and it got paid late."

McCaskill's campaign spokesman, Erik Dorey, said the senator immediately repaid the back property taxes — and even overpaid by $1,600 to cover all her bases.

"This petty political attack, planted by pathetically desperate Republican operatives over a simple misunderstanding that amounts to a couple hundred dollars and couple of weeks, is old news," said Dorsey.

He added that the attack was an attempt to distract from an extreme and underwhelming field of three Republicans vying to unseat McCaskill.

Republicans have already made a major issue out of unpaid back taxes McCaskill owed on a private plane. The first-term senator eventually repaid almost $300,000 and later sold the plane. Crossroads GPS, a Karl Rove-backed conservative outside group eager to oust McCaskill, launched ads in Missouri attacking her on the issue.

- This post was updated at 11:29 a.m.