There is a reason why elephants and donkeys don’t get along.

The Democratic National Committee stripped Connecticut Senator Joseph Lieberman ’64 LAW ’67 of his “superdelegate” status following his December endorsement of fellow senator John McCain of Arizona, a Republican, in this year’s presidential race. The move means that Lieberman — who has been persona non grata in the Democratic Party since losing renomination in the 2006 Democratic primary and subsequently winning re-election to the Senate as an independent — will be unable to cast a vote for the party’s nominee at the Democratic National Convention in August.

Democratic leaders at both the state and local levels said they are baffled at Lieberman’s decision to support a Republican but are unsurprised that the DNC has decided to deny him a vote at the convention.

“I’ve heard that from so many people who think Joe Lieberman just went too far outside the party tent when he endorsed a Republican,” Connecticut Democratic Chairwoman Nancy DiNardo said Sunday. “He’s virtually turned his back on friends who did a lot for him over so many years.”

Lieberman’s endorsement puts him at odds with a statement he made in a July 2006 debate against primary challenger Edward “Ned” Lamont SOM ’80. At the time, Lieberman pledged to support a Democrat for president in the 2008 election.

But Lieberman defended his endorsement in a Feb. 3 New York Post column, citing the need for bipartisan cooperation in the face of threats from Islamist terrorists.

“I know that it is unusual for someone like me — an Independent Democrat — to support a Republican candidate for president,” he wrote. “But the dangers we face as a nation are too profound … for us to let partisan politics decide who we will support.”

Lieberman’s Washington, D.C., and Connecticut offices could not be reached for comment over the weekend.

Lieberman, who has earned a reputation for working with politicians on both sides of the aisle during his 20 years in Washington, has co-authored legislation with McCain on several occasions, most recently on global warming regulations. In 2001, the two senators wrote the Gun Show Looping Closing and Gun Law Enforcement Act together.

“There is no doubt that [Lieberman] is more closely aligned to McCain than anyone [else] running for president,” a senior McCain advisor told the Wall Street Journal in December.

Lieberman has campaigned with the Arizona senator since making his endorsement late last year, including an appearance at a Sacred Heart University rally in Fairfield eight days ago. McCain, who also had the backing of all the major Republicans in the state — among them, Gov. M. Jodi Rell and Congressman Christopher Shays — won the Nutmeg State primary handily.

Given that level of involvement in McCain’s campaign, Lieberman should not be given a vote in choosing the Democratic nominee, Democratic Town Committee chair Susan Voigt said Sunday.

“I’ve always personally liked [Lieberman],” she said. “I don’t want to say he’s not entitled to support John McCain, but it doesn’t make sense for him to be a delegate now at the Democratic National Convention.”

Yale College Democrats President Ben Shaffer ’09 agreed, arguing that only those supporting Democratic candidates should be allowed to cast votes for the party’s nominee.

“When a high-profiled Democrat makes an endorsement of Republican presidential candidate, it would be silly for him not to expect consequences,” he said.

The Yale College Democrats stayed neutral during the 2006 senatorial primary but endorsed Lamont in the November general election, when Lieberman ran on the ticket of the newly created Connecticut for Lieberman Party.

Now in his fourth term in the Senate, Lieberman lists his affiliation as “Independent Democrat.” He caucuses with Senate Democrats and generally votes with the party, although he has been a vocal defender of the war in Iraq since the 2003 invasion.

Kathryn Baldwin ’09, president of the Yale College Republicans, said she finds the superdelegate system “odd” and that this stripping law illustrates the flaws of the Democrat nomination system, such as putting too much power in the hands of a few legislators.

“It makes me admire Lieberman a little bit more for crossing and voting for another candidate if he is willing to give up his status for it,” she said.

Superdelegates — who, unlike delegates chosen in state primaries and caucuses, are free to support whomever they want — comprise Democratic governors, members of Congress and members of the DNC. The Republicans do not employ a superdelegate system.

Lieberman officially lost his superdelegate status under the Democratic Party’s “Zell Miller rule.” Named for the former Georgia senator and governor who endorsed President George W. Bush ’68 in 2004 and delivered the keynote address at the Republican National Convention, the rule stipulates that all Democratic Party delegates who support a candidate of a different party shall be stripped of their delegate status.

With Lieberman gone, Connecticut currently has 11 superdelegates to the convention, six of whom have declared their support for Obama and one of whom who is backing Clinton. The other five have not yet endorsed a candidate.

—The Associated Press contributed reporting