They didn't endorse anyone for POTUS in 2008 because no one got a super-majority of votes cast but this year Bernie got a whopping 87.9%!!!.
"DFA, which was started by backers of former Vermont Governor Howard Deans 2004 presidential bid, has grown into a well-regarded grassroots political and issue-advocacy organization with active groups in states across the country and a track record of backing progressive candidates at the local, state and federal levels. Early in the 2016 race, the group urged Massachusetts Senator Elizabeth Warren to seek the Democratic nomination. This month, it conducted a national poll of members that concluded December 15. Sanders won 87.9 percent of the 271,527 votes cast in a contest where an endorsement could only be secured with a super-majority (66.67 percent or more) of all the votes cast. Clinton (who is backed by Howard Dean) took 10.3 percent, while 1.1. percent backed Maryland Governor Martin OMalley.
The level of support for Sanders was unprecedented. When the 11-year-old group held a similar vote on whether to endorse in the 2008 presidential race, no candidate cleared the super-majority hurdle.
This year however, 87.9 percent of Democracy for America members voted for Sanders in a national poll.
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Chamberlain explained that well immediately start organizing on behalf of Bernie in key primary states, from Iowa, New Hampshire, South Carolina, and Nevada to nearly a dozen states voting on Super Tuesday.
http://www.thenation.com/article/democracy-for-america-communications-workers-union-endorse-bernie-sanders/