WASHINGTON

When Republican Rand Paul was elected to the Senate in November, he received a congratulatory call from an unexpected source: U.S. Sen. Al Franken.

That 30-minute phone call -- the only one Paul received from a Democrat after Election Day -- has sparked an unlikely friendship between the Kentucky Tea Party conservative and an unapologetic Minnesota liberal. Franken attended Paul's party after he was sworn in as a senator, and Paul asked Franken to be his Democratic Senate mentor.

The duo has raised eyebrows because the two senators couldn't be further apart politically: Paul is a staunch libertarian and founded the Senate Tea Party Caucus, while Franken's liberalism is well known through his writing and speeches.

"At first blush, obviously it is [odd]," Franken said in an interview. "But in many ways it makes a lot of sense."

The pair's budding friendship serves as one small counterpoint to the notion that Washington's rhetoric is so toxic in today's hyper-partisan political environment that senators as dissimilar as Franken and Paul cannot come together.

Their role-playing as the Senate's odd couple follows in a long line of senators with some of the sharpest partisan stripes finding friends across the aisle, from former Sen. Edward Kennedy of Massachusetts and Utah's Orrin Hatch to Minnesota's Paul Wellstone and former New Mexico Sen. Pete Domenici.

"You can be friends and not necessarily agree on every political issue," Paul said. "I don't think people want us to always agree and sing 'Kumbaya.' They want us to disagree on issues of substance, and I think this may be an example of how we can show that the rhetoric doesn't have to always be inflamed."

While Franken and Paul disagree on most everything -- Paul joked on David Letterman's show that they'd try to set a record for voting the opposite way -- both say they can find common ground on cutting military spending or scaling back the Patriot Act.

Those issues are similar to what Paul's father, 2008 presidential candidate Rep. Ron Paul, has teamed up on with another well-known Democrat, Massachusetts Rep. Barney Frank.

Beyond their obvious policy differences, Franken and Paul share some common traits, most notably their path to Washington. Both ran campaigns that received intense national interest: Franken as a former "Saturday Night Live" writer and Paul as the son of a 2008 presidential candidate.

"Those guys carry with them some amount of their own celebrity -- they're not blend-in kind of guys," said Scott Jennings, a Kentucky GOP strategist. "They both have a kind of celebrity personality that surrounds them that's a little unusual."

Different Senate paths

While Paul and Franken both came to Washington amid plenty of fanfare, only one has sought the spotlight.

In a previous life, Franken might have been cracking "aqua Buddha" jokes at Paul's expense, one of the election's most-publicized stories about Paul's college days. But in the Senate, Franken has avoided the spotlight, keeping his head down in a style that many compare to then-U.S. Sen. Hillary Clinton in 2001. He generally doesn't talk to the national press and turns down cable TV interview requests.

Paul, meanwhile, has embraced the limelight. He wrote a book titled "The Tea Party Goes to Washington" and has made appearances on "The Daily Show" and the "Late Show With David Letterman."

Letterman, who called Franken a mutual friend, asked Paul if the Minnesota Democrat advised him about going on the show. "Yeah, he said don't," Paul responded.

An accidental phone call

Franken and Paul might never have bonded if not for Franken's mistaken notion of Senate etiquette.

The day after the election he called all the winning senators, Democrat and Republican. "I just thought that's what you do," Franken said. "Evidently, it isn't."

Franken and Paul hit it off, which Paul attributes to a similar sense of humor. First they talked about some Senate procedure, Franken said. "Then we talked about the fact he was an ophthalmologist, and I had the beginnings of some cataracts."

Paul was asked to choose a Democratic and Republican mentor shortly after being sworn in as part of the Senate's freshman orientation. He picked U.S. Sen. Kay Bailey Hutchison of Texas, and Franken.

In their first mentor meeting this month, Franken said he and Paul discussed working on legislation together, though nothing concrete was planned. Even on issues where Franken's liberalism and Paul's libertarianism intersect -- reducing military funding, for instance -- the two men are likely to reach the same conclusion from opposite ends.

In other words, don't expect Franken to join the Tea Party anytime soon.

Last month, Paul gave a speech on the Senate floor advocating cuts to Federal Aviation Administration funding while Franken presided over the chamber.

"He came up afterward and he was very complimentary," Paul recalled. "I said, 'Well, did I convince you? Did I get you to vote on my side?'"

"Oh, no," Franken told him.