Politico reported Saturday Clinton called Biden a "purposeful and dynamic" person.
Clinton said Biden will "help Senator Obama both win the presidency and govern this great country.
Howard Wolfson, who ran Clinton's bid for the Democratic presidential nomination, said Clinton's supporters would support the Obama-Biden ticket.
Wolfson added the question remains "whether Joe Biden is willing to go after (Republican presidential hopeful) John McCain."
Polls suggest only about half of former Clinton voters say they'll back Obama in November, Politico reported.
"I don't think this will either antagonize or assuage her supporters," Wolfson said. "Senator Clinton likes Joe Biden, and I don't think he said a bad word about her during the entire campaign -- there's no animosity or enmity at all -- in that sense he's a safe pick ... . But she's the only person who was going to automatically bring her supporters back into the fold."