Sen. Lindsey Graham, the South Carolina Republican who holds the seat that belonged for nearly fifty years to Strom Thurmond, is on the warpath this campaign season—against his own party.

Graham took exception to ads being run against Democratic senators who voted to continue foreign aid to Libya, Egypt and Pakistan. American embassies were attacked in the first two countries; someone who helped U.S. authorities find Osama bin Laden has been detained in the third.

The commercials in question were paid for by the political action committee of Graham’s Republican colleague, Sen. Rand Paul of Kentucky. Paul was weighing in on behalf of struggling GOP challengers in battleground states that are still in play in the presidential election.

Graham, by contrast, held a conference call with West Virginia’s Democratic Sen. Joe Manchin to tout bipartisan support for foreign aid. “Foreign relations are not a Democrat or Republican issue, but an American issue,” he insisted.

Replies Rand Paul: “I don’t see myself campaigning against a Republican in a general election ever, that’s why I think it’s extraordinary that Graham is supporting a Democrat in a general election.”

The battle lines are drawn. The Club for Growth’s president already hinted in September that Graham would be on the conservative pressure group’s target list. “If you are looking over the horizon of 2014,” he told a Christian Science Monitor breakfast, “the sun may rise over South Carolina.” Tea Partiers are anxious to collect another Republican establishment scalp.”

Constitutionalists and libertarians have long objected to Graham’s voting record. The senator has been a reliable champion of wars of choice, amnesty for illegal immigrants, cap and trade, the National Defense Authorization Act, and the Troubled Asset Relief Program.

So committed is Graham to preventing cuts in defense spending that he was willing to put tax revenues—and Grover Norquist’s Taxpayer Protection Pledge—on the table to protect the Pentagon. He is always on the lookout for “isolationism” within the Republican Party, detecting this phenomenon might be at work even in the Romney campaign’s Afghanistan posturing.

A Public Policy Polling survey last year found that 42 percent of South Carolina Republicans—and 53 percent of state Republicans who consider themselves conservative—regard Graham as too liberal. Local Republicans have repeatedly adopted resolutions critical of some of their senator’s votes.

The coalition is there to repeat recent successful primary challenges: economic and social conservatives allied with libertarians one on side, the Republican establishment and the neoconservatives on the other.

But Graham won’t be an easy man to bring down. First, South Carolina is a military-heavy state. Despite its conservatism, it is also the place that saved the candidacies of George H.W. Bush, Bob Dole, George W. Bush, and John McCain from (mostly) conservative insurgents.

Second, Graham is aligned with John McCain. McCain was also high on the Tea Party target list and faced a politically experienced challenger in former Congressman J.D. Hayworth. Stung by his loss in the 2000 Republican presidential primaries and the conservative reaction to his McCain-Feingold campaign finance reform, his voting record briefly veered to the left of Graham’s, almost entering Lincoln Chafee territory.

McCain nevertheless prevailed. He went negative on Hayworth early and often. He adjusted his voting record and issue positions where possible. He never for a moment took the Republican nomination for granted, unlike defeated GOP incumbents Richard Lugar and Robert Bennett.

Neither will Graham. Although he loves bipartisanship and Senate deal-making, he is also a natural fighter who will not shy away from political combat. Jeered by conservative critics at the Republican state convention in 2009, many of them Ron Paul supporters, he told them if they didn’t want to follow him to victory they were welcome to find the exit.

“I’m a winner, pal,” Graham chided a conservative delegate who tried to shout him down. “I’m not going to give this party over to people who can’t win.”

Graham easily defeated a conservative primary challenger in 2008. He also topped a Ron Paul supporter who managed to claim the Democratic ballot line to run against him in the general election.

We’ll see if he keeps up that winning track record in 2014.

W. James Antle III is editor of the Daily Caller News Foundation and a contributing editor to The American Conservative. Follow him on Twitter.