Sen. Lindsey Graham of South Carolina has an 89.12 lifetime rating from the American Conservative Union and has been in Congress since 1995. Yet the Republican fixture on Capitol Hill will face four primary challengers next year, all of whom accuse him of not being a true conservative.

Graham, who is much in the mold of his friend, Sen. John McCain, R-Ariz., is known for often reaching across the aisle on important legislative issues. One notable example of this is his being a member of the bipartisan Gang of Eight immigration reform group this year.

Before being elected to the Senate, Graham, a veteran of the U.S. Air Force Reserve, previously served as a member of the House of Representatives from 1995 to 2003.

"When a senator consistently gets pulled across the aisle and votes for legislation his Republican colleagues don't vote for, you begin to question his judgment," challenger Richard Cash said in an interview with ABC News. "People don't trust him anymore."

Bill Connor, a former candidate for South Carolina lieutenant governor who's also challenging Graham, said much the same thing. "You don't vote to defund Obamacare, and then vote for cloture on a bill to keep funding it," said Connor, who also criticized Graham for putting ads in South Carolina showing his opposition to the Affordable Care Act. "That's not being honest or showing character."

Graham joins the likes of Senate Majority Leader Mitch McConnell, R-Ky., Sen. Lamar Alexander, R-Tenn., and other prominent Republican Senators who are being challenged on their right flank this upcoming election season.

South Carolina Republican consultant Chip Felkel doesn't believe the claims questioning Graham's conservatism hold much water. "Their issues have to do with his ability, and his willingness to actually work with the other side without demonization, a trait I don't see coming from at least three of the four challengers," Felkel told ABC News. "His conservative voting record is pretty clear for those who will look."

Graham's opponents aren't buying it.

"While Senator Graham claims to be a 'pro-life senator,' the only evidence he can point to is a bill he supported when he was in the House," says South Carolina State Senator Lee Bright. "He can suddenly pretend to be a conservative, but none of this changes what he has become over the years: a creature of Washington."

For his part, Graham has very recently proposed some conservative initiatives. The most notable would be his proposal to ban abortion nationwide for unborn children at the age of 20 weeks post fertilization. In addition, Graham has said he's willing to hold up high-profile Obama Administration nominees, like Jeh Johnson and Janet Yellen, until he's allowed to speak with survivors of the 2012 attacks in Benghazi.

Business consultant Nancy Mace is the only woman to challenge Graham. "Graham has a record of supporting tax increases and he enthusiastically supported both of Obama's Supreme Court nominees, Elena Kagan and Sonia Sotomayor," says Mace. "Graham also supported the bailouts, and was the only Republican in South Carolina's congressional delegation to support the president's most recent debt ceiling hike."

When reached by ABC News, Graham didn't echo any sense of concern over the allegations being levied at him by his opponents. "We'll have plenty of time to talk about my record of being a conservative and what I've done for the conservative movement and I look forward to the contest - I'm not really worried about my election right now," said Graham.

Graham also expressed confidence that Republican senators facing primary challengers, including himself, would ultimately come out victorious in 2014. "I think Mitch, myself, Lamar represent Ronald Reagan type conservatism and I think that's going to do very well in 2014," said Graham.

Even this early in the race, however, Graham is getting high marks for his political acumen.

"Lindsey Graham has always been a good broken field runner," says former Rep. John Spratt, Jr., D-S.C. "He has tacked to the right on defense issues and foreign policy, and back to the center on judicial appointments. If there is a philosophy here, it is not called conservatism or liberalism; it's called pragmatism."

Spratt, a casualty of the 2010 Tea Party insurgency, thinks that ultimately the positions taken by the Republican Party in recent years have changed the dynamic for Graham in 2014, regardless of the eventual outcome.

"Tea Party types want more," says Spratt. "Lindsey Graham is clearly trying to move more to the right, but the problem is that his party's right wing have already moved, big time, in that direction."