In 2010, veteran Sen. Lindsey Graham (R-S.C.) predicted the then-booming Tea Party movement would "die out." He has been at odds with the small-government activists ever since. Graham has clashed with Tea Party favorites in the Senate, including Rand Paul of Kentucky and Mike Lee of Utah, over everything from his more interventionist foreign policy to his hinting that taxes might be raised as part of a grand bargain on the budget.

Lately, Graham's advocacy of a new immigration reform effort — which includes a path to legal status for some people who came to the U.S. illegally — has drawn particular ire from Graham's enemies. National Tea Party leaders say they've had enough, and they're vowing to push Graham aside when he runs for re-election next year. "He's begging for a primary," Matt Kibbe, president of FreedomWorks, told ABC News this week.

How worried should Graham be? He probably shouldn't push the panic button yet, but he should take the grumbling seriously. Graham has already raised $5.4 million — second only to Senate Minority Leader Mitch McConnell (R-Ky.) among incumbents up for reelection this cycle, says Stacy Kaper at National Journal. "Still, there is ample reason for Graham to be wary":

The conservative Club for Growth has picked Graham as a top target for 2014 and is closely monitoring his votes and the candidates who enter his primary field. Groups opposed to immigration reform, such as NumbersUSA, are running ads against Graham in South Carolina.

And last weekend, a loud but unsuccessful band of tea-party loyalists and libertarians tried to thwart the senator's path to reelection with an attempt to change the rules governing how state Republicans pick their candidate.

It all appears to have taken a toll. An April Winthrop poll found that Graham's approval rating among Republicans and Republican-leaning independents had dropped to 58 percent, down from 72 percent in February. [National Journal]

The people demanding Graham's political scalp shouldn't get their hopes up, though. It might just be that the naysayers are, at the moment, more vocal than Graham's supporters: "The 30-odd percent of South Carolina Republicans who don't approve of the job he's doing, well, they really don't approve," says Betsy Woodruff at National Review. But their anger won't necessarily get Graham out of office. Their problem: "Lindsey Graham is very popular in his home state," with longstanding approval ratings. People might be lining up to run against Graham, but none of the potential challengers has particularly "rosy prospects," says Woodruff.

Long shot or no, some activists are determined to mount a real challenge. Graham deserves to get primaried, says Daniel A. Herrera at PolicyMic. His criticism of Rand Paul's filibuster — which aimed to expose how President Obama's drone policy threatens civil liberties — was a disgrace. "Those who are dedicated to restoring liberty back into the platform of the Republican Party should see this as a fantastic opportunity to oust an incumbent and elect someone who respects civil liberties and freedom," Herrera says.

Still, some people think a primary fight will harm Graham's detractors more than it will him. "By any definition, South Carolina Senator Lindsay Graham is a conservative," says Jamelle Bouie at The Washington Post. Yes, he has deviated slightly from hardliners climate change legislation and higher taxes, says Bouie, but we're talking about small deviations. "On almost everything else, Graham sides with the right flank of the GOP." His sin, it seems, is "his willingness to compromise and legislate," adds Bouie, which says more about the dysfunction plaguing the GOP than it does about Graham.