Perhaps even more disconcerting for Graham, who is staring at a GOP primary in 2014, is his steep drop among Republican voters in South Carolina. The latest survey from Winthrop showed 45 percent of Republican voters approving of Graham, compared with 40 percent who disapprove.
Those mediocre numbers represent a massive decline since February, when nearly 72 percent of GOP voters said they approved of Graham. In Winthrop's April survey, about 57 percent of Palmetto State Republicans approved of Graham.
Three Republicans have already announced their intention to challenge Graham next year.
Graham has done his part to placate the most conservative faction of his party, vowing earlier this week to block every Obama administration appointee until survivors of the 2012 attack in Benghazi testify before Congress.
This post has been updated.