A red-state Republican senator up for reelection and seen as vulnerable to a primary challenge from the right embraces a plan to allow illegal immigrants to gain U.S. citizenship — a lightning rod for GOP primary voters if there ever was one.

Seems unthinkable on its face. Yet that’s precisely what Lindsey Graham did last week. And the remarkable thing is, there’s no sign of a backlash in his home state, South Carolina — at least not yet.

It’s a reflection of both Graham’s political strength and his party’s rapid evolution on immigration since its November licking among Latinos.

Long viewed with suspicion among the right wing — in no small part because of his 2007 endorsement of the Kennedy-McCain immigration reform bill — Graham apparently feels safe enough heading into 2014 to stick his neck out again on a politically perilous debate he obviously cares about deeply.