Lindsey Graham's numbers slip with primary voters

Sen. Lindsey GrahamLindsey Olin GrahamTop Louisiana health official rips Cassidy over ObamaCare repeal bill Senate Dems hold floor talk-a-thon against latest ObamaCare repeal bill Overnight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions MORE's (R-S.C.) approval numbers have taken a major dip with Republican primary voters, according to a new poll from Winthrop University.

Graham's approval rating has slipped to 45 percent in the poll, a major drop from his 72 percent rating in February. His disapproval rating with Republicans and GOP-leaning independents has spiked to 40 percent.

Those numbers should be a cause for concern with longtime senator, who is facing primary challenges from a number of second-tier candidates. His approval ratings drop coincides with his work to pass comprehensive immigration reform and vocal criticism of the tactics of Republicans whose push to defund ObamaCare caused the government shutdown.

Conservative outside groups have indicated they'd like to target Graham, but it's unclear if any of the candidates challenging him will be up to the task of giving him a tough race. He has more than $7 million in the bank for his reelection, while none of his opponents has been able to get traction in the money race or make it clear why they should be the one to face him in the primary runoff.

The poll of 887 South Carolina residents was conducted from Oct. 19-27 and has a margin of error of plus or minus 3.3 percent.