Cleland has shown no interest in the seat, which he lost in 2002, while Barrow hasn't ruled out a bid. Broun is the only Republican who's officially announced a bid for the seat, though the other Republicans who were polled are also mulling bids.

The GOP primary field is unsettled at best at this point: no potential candidate pulls more than 15 percent support in a hypothetical match-up.

The automated poll of 602 voters and 366 likely GOP primary voters was conducted from Feb. 15-18 and has a margin of error of 4 percent for the overall poll and 5.1 percent for the GOP primary subset.

—This post was updated at 2:50 p.m.