NASHVILLE (AP) — A national conservative group is attacking former Tennessee Republican Gov. Bill Haslam as he considers running for another open U.S. Senate seat.

The Club for Growth has launched a website and a 60-second web ad mostly targeting the popular two-term governor over the federal investigation into a diesel rebate scam at his family's truck stop chain, Pilot Flying J.

The Haslams haven't been charged with wrongdoing in the investigation, which has spurred more than a dozen convictions at Pilot.

The Club for Growth has encouraged Republican Congressman Mark Green to run in 2020 for the seat held by GOP Sen. Lamar Alexander, who is retiring.

The group criticized Haslam in 2017 before he decided against running to replace now-retired Republican Sen. Bob Corker. Republican Marsha Blackburn won that 2018 race.