Sen. Bob Corker (R-Tenn.) might be vulnerable to a challenge from the right in 2012, but who would make a stand strong enough to defeat him is unclear, according to a new poll from the Democratic firm Public Policy Polling.

The survey found 43 percent of Republican primary voters wanted to nominate a candidate more conservative than the incumbent next year. Yet potential opponents, including country singer Hank Williams Jr. and Rep. Marsha Blackburn, trail Corker, according to the survey.

Neither seems to be making serious moves toward a Senate race, though. Blackburn has already said publicly that she would not run, and though Williams has toyed with the idea of a Senate run in the past, he hasn’t signaled interest.

In another encouraging sign for the former mayor of Chattanooga, 60 percent of Republican voters approved of the job Corker is doing in the Senate, while only 19 percent disapproved and 20 percent were not sure.

PPP surveyed 400 Tennessee Republican primary voters Feb. 9-13, and the poll had a margin of error of 4.9 points.