Centrist Sen. Jon Tester was among the Democratic rock stars of the 2006 midterms, flipping a U.S. Senate seat in a deep red state and going on to win reelection in 2012 and 2018. But GOP nominee Tim Sheehy, endorsed by former President Donald Trump, may prevent Tester from winning a fourth term in 2024: the incumbent Democrat trails him by 6 percent in a Fabrizio poll released in late August. Sheehy has been touting his military record on the campaign trail. But according to reporting from The Guardian’s Martin Pengelly, Sheehy “appears to have failed to follow Pentagon rules for clearing por…