Although candidate filing is about six weeks away, U.S. Sen. Roy Blunt and his Democratic opponent, Secretary of State Jason Kander, are already weathering repeated political attacks.

Rather than focus on their campaigns, many of the criticisms are aimed at damaging their character by challenging how they are handling their offices.

Republicans are faulting Kander for some of the findings in a recent state audit, which questions how he had handled staff raises and how his office had misfiled $120,000. Meanwhile, Democrats continue to jab at Blunt’s apparent increased use of charter planes, which cost taxpayers more than if he traveled by car.

Neither Blunt nor Kander, by the way, is accused of anything illegal.

Dave Robertson, head of the political science department at the University of Missouri-St. Louis, says the attacks are exploratory.

“Both candidates are shadow-boxing to find vulnerabilities in their opponent,” he said. “So it’s not too surprising that they’re trying out different arguments on each other, in an effort to get a little bit of an advantage, even this early.”

Missouri’s Senate contest, Robertson said, is among a dozen or so nationally that could help determine which party controls the U.S. Senate after this fall’s election.

The sharpest attacks, by the way, are coming from the state parties or outside political groups. The candidates themselves have yet to engage.

Planes often a political target

Democrats continue to track Blunt’s increased use of charter planes.

According to the Secretary of the Senate’s records, Blunt appears to have preferred land travel when he toured the state during his first three years in the Senate.

But since 2014, he has chosen charter planes for at least 12 days of travel, which have cost about $60,000 more than if the senator had driven. The flights have been paid by taxpayers since the visits were official ones.

“Apparently Sen. Blunt believes that the best use of tax dollars is traveling in luxury to get to all of his events in Missouri so he can get back to Washington as quickly as possible,” said Will Baskin-Gerwitz, Missouri Democratic Party spokesman,

The senator's staff notes that Blunt could not have made as many stops if he’d traveled by car – a fact that prompts Gov. Jay Nixon and U.S. Sen. Claire McCaskill, both Democrats, to often fly as well. (Both have periodically weathered their own political attacks over the practice.)

Blunt most recently has been flying around the state to examine the flood damage. “Planes, trains and automobiles,’’ quipped Blunt spokesman Brian Hart. “He’s traveling the state and will continue to travel the state.”

Hart said that the senator has held 1,500 official stops in the state since he became senator in 2011, visiting each of the state’s 114 counties at least twice.

Hart emphasized that the senator’s charter flights have involved public companies available to anybody, were not luxurious and that Blunt had eschewed using any donated flights provided by donors.

State audit generally positive

Missouri Auditor Nicole Galloway, a fellow Democrat, issued the scheduled audit last week of Kander’s office.

Although the audit gave his office an overall performance rating of “good,’’ it had zeroed in on a couple of problems.

The audit summary said that Kander’s Business Service Division “did not have adequate controls and procedures in place to record electronic payments.”

The audit also concluded that Kander’s office had incorrectly deposited $120,000 over the past three years into the state’s general-revenue fund instead of the secretary of state’s Technology Trust Fund, where the money apparently was to be parked.

The other issue involved Kander’s raises to several dozen employees, which the audit said had not been appropriately documented.

The newly formed conservative group Missouri Rising accused Kander of “money mismanagement.”

Missouri Rising executive director Brian Rogers said in a statement that the audit raised question about whether Kander "can be trusted to properly handle taxpayers’ dollars.”

Kander spokeswoman Stephanie Fleming contended that the GOP attacks represented “a gross mischaracterization of the audit, as Secretary Kander has cut over $200,000 in salaries and 11 positions since taking office, and this year he submitted the smallest general revenue operating budget for a secretary of state’s office since 1998.”

She blamed the misfiling of the $120,000 on “a technical glitch” by his predecessor, fellow Democrat Robin Carnahan, that had gone on for years. “It has been addressed,’’ Fleming said.

Robertson predicted that political sparring directed at Blunt and Kander will continue, and possibly heighten as candidate-filing gets closer. Filing will begin Feb. 23, and continue through March 29.

Their latest campaign-finance reports will be due later this month.