Sen. Lindsey Graham’s (R-S.C.) support for a path to citizenship for illegal immigrants could soon be put to the test in the form of a primary challenge.

South Carolina Republican National Committeeman and party activist Dr. Walter “Buddy” Witherspoon said Tuesday that he has formed an exploratory committee and was on his way to Washington to gauge support in the coming days for a run at Graham’s seat.

Witherspoon said he will not announce anything this week but could potentially make a decision public before the end of the year. He has until March to decide whether he wants to run.

If he were to enter the race officially, he would have to give up his position with the Republican National Committee (RNC).

Recent polls show Graham is popular among the entire electorate, including Democrats, but his weaker numbers among Republicans suggest he could be susceptible to a strong primary challenge focused on illegal immigration.

Graham caused a stir among conservatives by backing an immigration bill that included a path to citizenship earlier this year. Witherspoon is a religious conservative who casts himself as someone who will fight his own party for conservative principles.

Witherspoon is an orthodontist who was elected South Carolina’s committeeman in 1996 and has been active behind the scenes in state party politics for years, but he has never run for elective office.

Graham has more than $4 million in his campaign account and no serious challengers yet. He was elected in 2002 to succeed Sen. Strom Thurmond (R-S.C.), taking 54 percent of the vote.

Since then, he has carved out a centrist voting record that has made him a prime candidate for a primary challenge in a Southern state.

A June InsiderAdvantage poll showed his disapproval rating higher among Republicans (46 percent) than Democrats (30 percent), while his approval among both was in the low 30s. The poll was conducted soon after Graham took ownership of the immigration bill — a severely unpopular position in the state, according to the poll.

But even supporters of a primary challenge concede Graham is well-liked and it will be tough to unseat him, especially for an unknown like Witherspoon. The race is not a top pickup opportunity for Democrats.

Graham did not seem concerned about the prospective challenge Tuesday.

“I look forward to running for reelection based on being a very effective senator and look forward to comparing my ability to represent the state with anybody, including Mr. Witherspoon,” Graham said.

South Carolina GOP Chairman Katon Dawson, who had also been rumored as a possible Graham primary challenger, said Graham and Witherspoon both appeared at a fundraiser Monday night for the Lexington County Republican Party.

Dawson said Graham was “very well-received by the audience” but acknowledged a volatile climate in the state.

“It’s a political environment where people are uneasy, whether it be $3.50 for a gallon of gasoline or the immigration debate or future Supreme Court justices,” Dawson said.

Neal Thigpen, a Republican activist and professor at Francis Marion University in Florence, S.C., was dubious that Witherspoon could give Graham a significant challenge.

Thigpen, who has given money to Graham and acknowledged he doesn’t see eye to eye with the “religious right,” said the immigration issue isn’t as strong as it was several months ago.

“I would have to say, with a bunch of these trench-level Republicans that were irritated with Lindsey, particularly with that immigration bill, I think some of that animus has subsided,” Thigpen said.

While not focusing exclusively on immigration, Witherspoon made it clear his challenge would come from the right on a number of issues and key on border enforcement.

He has launched a website at buddywitherspoon.com.

“My interest is naturally with all that’s going on in the nation and with the sovereignty of our nation and our Constitution,” he said. “I’m just very concerned. This is certainly not an ego thing.”

A spokeswoman for the National Republican Senatorial Committee, Rebecca Fisher, said: “Voters of South Carolina strongly support Sen. Graham and all he has done for the state. We are confident he will be easily reelected next November.”

A potential vulnerability for Witherspoon is his former ties to a group labeled by some as racist.

In 1999, then-RNC Chairman Jim Nicholson asked Witherspoon to leave the Council of Conservative Citizens.

Witherspoon initially refused but later relented.

Sen. Trent Lott (R-Miss.) and former Rep. Robert Barr (R-Ga.) were also forced to sever ties to the group.