Those decisions, a report by Politico says, were based on individual observations, such as the superdelegate in Minnesota who initially favored Hillary Clinton but was swayed by Barack Obama's 12-primary win streak.
A Colorado superdelegate was reportedly put off by Clinton's Senate vote authorizing military force in Iraq.
There was the 21-year-old Marquette University student, the youngest person ever elected to the Democratic National Committee, left cold by Clinton's reliance on old establishment ties.
Nothing against Clinton, he told Politico, but, "My generation was overwhelmingly speaking in support of him (Obama), and that's the reason I went with him."
U.S. Rep. George Miller, D-Calif., said many of his colleagues put re-election concerns above everything else.
Civil rights leader Rep. John Lewis, D-Ga., endorsed Clinton in October 2007 but switched sides in late February, after Democrats in his district threw their support behind Obama.
Clinton looked like a shoo-in, early on, the report said, leading in superdelegates 169-63. according to surveys in November.
But, as Obama began piling up state after state in February, the superdelegates started swinging hard toward him. Surveys show Obama picked up 51 superdelegates between Super Tuesday on Feb. 5 and the primaries in Texas and Ohio on March 4, Politico said.