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 ScottTimothy (Tim) Eugene ScottPartisan tensions rise as Mueller bill delayed GOP dismisses report that tax law will add .9 trillion to debt Gowdy on video questions how long Pruitt is ‘going to make it’ 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 GowdyHarold (Trey) Watson GowdyCambridge Analytica whistleblower briefs House Dems GOP chairmen say they have deal with Justice on documents Overnight Energy: Dems raise new questions about Pruitt's security | EPA rules burning wood is carbon neutral | Fourth GOP lawmaker calls for Pruitt's ouster | Court blocks delay to car efficiency fines 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.