In a political body like the Senate, fraternal tensions are par for the course. Although Lieberman's actions are unusual, Zell Miller, a conservative Democratic senator from Georgia, infuriated his party by endorsing President Bush for reelection and delivering a fiery keynote speech at the 2004 Republican convention.
Miller declined to comment for this article.
On the GOP side, former Sen. Lincoln Chafee, a moderate Republican from Rhode Island, irritated GOP leaders by breaking with the party on a number of issues, then voting in 2004 against Bush.
But two years later, the Senate GOP campaign committee tried -- unsuccessfully -- to help him win reelection in a year of Democratic gains.
Chafee suggested Lieberman's actions might be testing the Democrats' patience.
"How far can you take this independence and still break bread with the Democrats?" he asked.
Despite the history, retaliation has been rare.
"Senators have been reluctant to punish colleagues for straying from the party line," said John J. Pitney Jr., a professor of government at Claremont McKenna College.
On the other hand, Pitney said, "suppose Obama loses narrowly while Senate Democrats gain seats. At that point, Lieberman's critics will have both the motive and the means to punish him."
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richard.simon@latimes.com
