As Minority Leader Mitch McConnell (R-KY) says that he is in the "most difficult" re-election bid of his Senate career, The Hill also reports that Lindsey Graham (SC), one of the most prominent Republican proponents of the Senate's "grand bargain" immigration bill, has suffered a noteworthy drop in his approval rating:

Graham’s approval rating has sunk to 31 percent and he has a 40 percent disapproval rating, according to a poll released Friday by Atlanta-based InsiderAdvantage. The new poll points to Graham’s support for the Senate immigration bill, which includes a path to citizenship, as a likely reason for his apparent unpopularity.

His disapproval among Republicans is higher — 46 percent — than among Democrats —30 percent. Both give him an approval rating in the low 30s.

Only 21 percent of respondents approved of the immigration bill, while 63 percent disapproved. When asked whether they approved of Graham’s “efforts to reach a consensus among his colleagues” to pass the bill, 24 percent approved and 51 percent disapproved, including 57 percent of Republicans.

In November of 2006, Graham was at 56% approval. The Hill notes that this high disapproval amongst Republicans could make Graham vulnerable to a primary challenge.
(H/T Kaus)