The David and Charles Koch-backed political group Freedom Partners is so confident in Ohio Republican Sen. Rob Portman's reelection chances that they are cancelling a future ad buy in his state.

The group has spent close to $10 million in ads opposing Democratic challenger Ted Strickland. 

But recent polls show that despite the Republican presidential frontrunner's under-performance in Ohio, Portman is pulling ahead there. 

“Rob Portman has run one of the strongest campaigns of the cycle, he maintains a significant lead in virtually every poll, and the dynamics of the race have changed,” Freedom Partners spokesman James Davis said. 

“We will remain on air through Sept. 14 with our current ads, but given Portman's strong position in the race, we are going to drop the remaining reservation and reserve flexibility over future spending.”