Topeka ? A free-market political action committee is launching a television ad in the U.S. Senate race in Kansas attacking the independent challenger to three-term Republican incumbent Pat Roberts.

The Freedom Partners Action Fund says it is spending “six figures” on the ad against Greg Orman beginning Tuesday. The PAC is part of the political network of billionaire businessmen Charles and David Koch.

The 30-second spot notes that Orman contributed to President Barack Obama’s 2008 presidential campaign and to other Democrats. It says a vote for Orman is another vote for Obama.

Obama received 38 percent of the vote in GOP-leaning Kansas in 2012.

Orman is a 45-year-old Olathe businessman running as a centrist. His campaign called the ad misleading and released a list of his past contributions to GOP candidates.