Lindsey Graham’s collaboration with Democrats points to tea-party primary challenge in ’14

South Carolina Republican Sen. Lindsey Graham’s opposition to political ads targeting several Democratic senate incumbents could create a significant re-election issue for him in 2014.

When Kentucky Republican Sen. Rand Paul launched an ad campaign against Democrats who opposed his proposal to end foreign aid to Libya, Egypt and Pakistan, Graham took the unusual step of defending the Democrats from a fellow Republican.

Graham held a conference call with West Virginia Democratic Sen. Joe Manchin to slam both the ad and Paul’s foreign aid bill. (RELATED: Lindsey Graham defends Democrats from Rand Paul’s foreign aid attacks)

Paul swiftly fired back, telling Politico, “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.”

“Which is more important,” he asked: “Defending … a failed policy of foreign aid or getting a Republican majority?”

The firestorm comes amid speculation that Graham could be a tea party target when he faces re-election two years from now.

In September, Club for Growth president Chris Chocola told a Christian Science Monitor breakfast that his group may have Graham in its sights.

Noting several high-profile conservative primary victories over established Republican incumbents, Chocola said, “If you are looking over the horizon of 2014, the sun may rise over South Carolina.”

Last year a Public Policy Polling survey found that 42 percent of South Carolina Republicans believed Graham was too liberal. Among the two-thirds of state GOP primary voters who consider themselves conservative, that number was 53 percent.

Only 38 percent of self-described conservatives agreed that Graham’s views were “just right,” compared to 45 percent of all South Carolina Republicans.

South Carolina state Sen. Tom Davis, who has emerged as a local tea party favorite, believes a primary challenge is inevitable.

“I like Lindsey Graham,” Davis told The Daily Caller News Foundation in an interview. “I think he is a good guy and has done some good things.”

“[But] I look at some of the things he has done and not only me, but some other conservatives, are scratching our heads.”

Graham teamed with Arizona Republican Sen. John McCain on comprehensive immigration reform legislation conservatives widely regarded as amnesty for illegal immigrants.

The senator’s fiercest critics nickname him “Grahamnesty.”

Graham also voted to confirm both of President Barack Obama’s nominees to the Supreme Court, Justices Elena Kagan and Sonia Sotomayor.