Lieberman lost the 2006 Democratic Senate primary to Ned Lamont, and saw longtime friends such as Attorney General Richard Blumenthal (D) and Sen. Chris Dodd (D-Conn.) either endorse or campaign for Lamont that fall. Since his victory, Lieberman has caucused with Democrats, although he often frustrates the majority party by siding with Republicans on foreign policy and national security issues.

Lieberman could be a powerful ally by Crist's side in the Sunshine State. Not only does Lieberman have the ability to attract both Democratic and Republican votes, but his presence on the 2000 presidential ballot, as the Democratic vice presidential nominee, was credited by many political observers for the closeness of the race, particularly in Florida. Large swaths of Jewish voters live in South Florida, and are believed to have supported Lieberman strongly.

Endorsing Crist could be dangerous for Lieberman, too, as he would risk angering Democrats who support Rep. Kendrick Meek (D-Fla.), who's also running.

Lieberman said Crist asked for some advice, but wouldn't divulge details.

"We talked about odds and ends, just the nuts and bolts of campaigning, like what it's like and what questions you can expect," Lieberman said.

An endorsement wasn't specifically discussed, and Lieberman said he had no plans other than to stay in contact with Crist.

"I wish him well," Lieberman said. "We talked and just agreed to keep in touch."