U.S. Sen. Claire McCaskill’s tax problems might not be so inviting a political target for her opponents after all.

It turns out that the three Missouri Republicans hoping for the chance to unseat her in the fall have been slow payers, too, although their overdue bills were not as sizable.

But even more ironic is the case of GOP Senate hopeful John Brunner. Among his tardy tax payments was one involving his company plane, a situation similar to one that caused McCaskill — a first-term Democrat in a tough re-election battle — so many political headaches a year ago.

Indeed, her plane problems seemed destined to become a surefire Republican line of attack this fall, though it hasn’t played a major role during the Republican primary fight.

The Brunner campaign did raise the issue, however, in a news release earlier this year. It criticized McCaskill on several fronts and included a reference to a story in The Kansas City Star that mentioned “her failure to pay” taxes on the plane.

But St. Louis County tax records show that, should Brunner become the GOP nominee, he might need to be careful or avoid the issue altogether.

The plane involving Brunner was registered to Vi-Jon, a health and beauty care products manufacturer that he ran until 2009. Records show that the company was a little more than two months late paying the 2006 personal property tax bill for the plane. It paid $9,287 in taxes, interest and penalties in March 2007.

Brunner spokesman Todd Abrajano said that 2006 “was the first year that Vi-Jon owed property tax on the company plane and the company’s tax advisers unfortunately missed the filing deadline for that year. The oversight was corrected 68 days after the deadline and all taxes, penalties, and interest were paid in full.”

Personal property tax payments in Missouri are due by Dec. 31 of the tax year.

McCaskill’s plane problems were more involved and more expensive. They had to do with a private aircraft she owned jointly with her husband and several investors. She had been using it for official Senate business and billing taxpayers — which is allowed — but got into trouble when her office mistakenly also included political travel as well.

McCaskill repaid for the wrongly billed political travel, as well as for all the official trips that were legally billed, which she didn’t have to do. But then it turned out that the plane owners owed St. Louis County more than $300,000 for four years of back taxes, interest and penalties. McCaskill took responsibility for the error, paid the bill and her family since has sold the plane.

“Claire knows that mistakes can be embarrassing,” said McCaskill campaign spokeswoman Caitlin Legacki. “But Claire also understands that true leadership is taking accountability for honest mistakes and fixing them, not finding someone else to blame.”

Still, the plane was not the only issue involving late tax payments among McCaskill’s potential competition. All three Republicans running in the Aug. 7 Senate primary have been delinquent on occasion with their real estate taxes, county records show, as has McCaskill.

Republican candidates also have been late to pay taxes on their personal vehicles.

St. Louis County tax records show Brunner did not pay his 2007 and 2008 taxes on a Ford Five Hundred until April 2009. He paid $699 in back taxes, interest and penalties.

Like many Missourians, “including Sarah Steelman, Todd Akin, and Claire McCaskill, John Brunner has occasionally paid his property taxes late,” Abrajano said. “As a responsible citizen and taxpayer, John Brunner immediately paid all taxes, interest, and penalties in full as soon as the oversights were recognized.”

St. Louis County tax records show that U.S. Rep. Todd Akin, who also is a GOP candidate for Senate, did not pay taxes owed on his cars in 2001 or 2002 until July 2003. They were a 1985 Plymouth Voyager, a 1987 Honda Accord, a 1994 Ford van and a 1996 Chevrolet Blazer. His late bill was $584.

Akin’s $180 payment on the 2004 personal property tax bill for his vehicles also was nearly two weeks late. Campaign spokesman Ryan Hite said that Akin and his wife do their own taxes. The oversights, Hite said, were “found and resolved.”

Phelps County tax records show that Republican candidate Sarah Steelman was one month late paying her 2010 personal property taxes on three vehicles: a 2003 Dodge pickup, a 2003 Jeep Liberty and a 2008 Infinity QX56.

In a statement, Steelman, a former state treasurer, said: “Yes, I was a little late on paying the tax and as a result had a small additional fee. I accept full responsibility for the oversight. The error was mine.”