It's known as the Zell Miller rule.
Joe Lieberman's endorsement of Republican John McCain disqualifies him as a super-delegate to the Democratic National Convention according to Democratic State Chairwoman Nancy DiNardo.
Miller, then a Democratic senator from Georgia, not only endorsed Republican George Bush four years ago, but he delivered a vitriolic attack on Democrat John Kerry at the Republican National Convention. The Democrats responded with a rule disqualifying any Democrat who crosses the aisle from being a super delegate. Lieberman will not be replaced, DiNardo said.
Lieberman lost the Democratic nomination in 2006 and was re-elected as a petitioning candidate. He remains a registered Democrat and a member of the Senate Democratic caucus, but he declared himself an "Independent Democrat."
Connecticut has 12 super delegates: six Democratic National Committee members, one Democratic senator, four Democratic members of congress and one "unpledged add on" to be selected. Super delegates are not bound by a state's primary results.