Graham's approval rating with primary voters is at 66 percent, with 26 percent disapproving. He leads a generic "more conservative" Republican in the race by 51 to 40 percent, a big jump from the 37 to 52 percent position he was in when the pollster last checked slightly less than a year ago.

Graham's standing jumps when paired against actual Republicans who could theoretically challenge him. He leads Rep. Tim ScottTim ScottThe Hill's Whip List: Senate ObamaCare repeal bill Lawmakers celebrate National Selfie Day on Twitter GOP senators pleased with Ivanka Trump meeting on family leave, child tax credits MORE (R-S.C.), who may be picked to replace retiring Sen. Jim DeMint (R-S.C.), by 54 to 32 percent. He has a 57 to 29 percent edge over Rep. Trey GowdyTrey GowdyGowdy won't use Oversight gavel to probe Russia GOP rep Gowdy on healthcare bill: ‘I try really hard not to give the Senate advice’ Overnight Cybersecurity: Obama DHS chief defends Russian hack response | Trump huddles on grid security | Lawmakers warned about cyber threat to election systems MORE (R-S.C.), a 64 to 26 percent edge over former South Carolina Gov. Mark Sanford (R), a 64 to 20 percent edge over Rep. Mick Mulvaney (R-S.C.) and a 67 to 17 percent lead over state Sen. Tom Davis (R), who many have speculated will challenge Graham but recently told The Hill that he "probably" won't run for the seat.

While many Washington-based conservative groups want to see Graham challenged in the primary, these numbers (along with the possible chance to run for DeMint's seat) hint at why no one has yet signaled they will run against Graham.

The poll of 506 Republican primary voters was conducted from Dec. 7-9 and has a margin of error of plus or minus 4.4 percentage points.