In an interview, James Slepian, Renacci's top aide, said they last heard from federal authorities four or five months ago and that "neither campaign is the subject of any kind of investigation," but that investigators instead appeared to be looking into whether donors were improperly reimbursed. "To date we have been given no information by anyone that anything unusual or improper took place," Slepian said. But "if at any point that donations made to our campaign were made improperly, every dollar will be returned immediately." "The campaign is aware of the investigation and is fully cooperating," said Travis Considine, communications director for Mandel's campaign. "Neither the campaign nor anyone associated with it is a target of the investigation." Michael Puterbaugh, corporate counsel for Suarez Corporation, declined to speak about the matter. "We have a corporate policy that we don't respond any claims or allegations that haven't been publicly filed," he said. An FBI probe would be bad news for the GOP. Republican groups have spent millions to batter Brown on the airwaves, hoping Mandel can compete in the in the battleground state. And the Renacci-Sutton race is expected to be close, as well, with the two incumbents holding a combined $2 million in campaign cash at the end of March.