Sen. Jim Bunning further escalated his war of words against his own party’s leadership on Tuesday, as the Kentucky Republican threatened to sue the GOP’s campaign arm if it recruits someone to run against him in a primary next year.

Bunning vented his frustration with National Republican Senatorial Committee Chairman John Cornyn (Texas) during a conference call with Kentucky reporters, one day after the NRSC chief said the committee is supportive of Bunning and would back him if he were to get a primary challenge.

“I don’t believe anything John Cornyn says. I’ve had miscommunications with John Cornyn from, I guess, the first week of this current session of the Senate,” Bunning said, according to the Louisville Courier-Journal. “He either doesn’t understand English or he doesn’t understand direct: ‘I’m going to run,’ which I said to him in the cloakroom of our chamber.”

Bunning’s rant left high-level Republican operatives on Capitol Hill stunned Tuesday afternoon with some wondering how much damage the Senator’s hostility — or “paranoia” as one Republican described it — will do to his 2010 re-election campaign which, even at this early point in the cycle, already appears to be on the ropes.

Republican insiders in Washington, D.C., and in Kentucky have become increasingly concerned about Bunning’s viability as a candidate and their ability to hold the seat if he is the nominee. Bunning has repeatedly asserted that he’s running for another term, even as GOP leaders such as Senate Minority Leader Mitch McConnell (Ky.) and Cornyn have continued to signal that Bunning’s decision may not be final.

Last week, Kentucky state Senate President David Williams (R) met with NRSC officials about a possible 2010 Senate bid. The meeting has been described as a courtesy visit, and whether Williams would challenge Bunning in a primary or only run if Bunning steps aside remains to be seen.

Williams is a close friend and ally of McConnell, and according to KyPolitics.org, a blog that covers Bluegrass State politics, the meeting was arranged with the knowledge of high-level McConnell staffers. Kentucky Secretary of State Trey Grayson has also been mentioned as the GOP’s top choice to run for Senate if Bunning stepped aside.

Bunning said Tuesday that if the NRSC were involved in recruiting a candidate to run against him in a primary he would sue the committee for violating its bylaws.

“Support of incumbents is the only reason for [the NRSC’s] existence,” Bunning said. “So if they recruited someone and supported them in a primary against me, I would be able to sue them because they’re not following their bylaws.”

In response, NRSC spokeswoman Amber Wilkerson would only reiterate the committee’s support of Bunning.

“Sen. Cornyn has made it clear he supports Sen. Bunning’s bid for re-election, and he has no intention of recruiting a primary opponent against him.”

One Kentucky GOP insider said Bunning’s latest tirade will only serve to undermine the Senator in the place he needs help most right now, his campaign bank account.

Talk of a possible Bunning retirement began heating up at the end of January when he reported a paltry $150,000 in his campaign account at the end of 2008. In response, Bunning said he has two major fundraisers planned for April and set a goal of $2 million raised by the end of the second quarter.

But the Kentucky insider said Tuesday that Bunning’s tirades are only serving to “destroy his reputation” with donors.

“All the anecdotal evidence is that fundraising is not going well” for Bunning, the insider said. “We’ll see in the [first-quarter] report.”