The latest influential Democrat to abandon neutrality is former Michigan Congressman David Bonior.
Bonior, who ran John Edwards' 2008 presidential bid, will declare his support for Obama today, ABC News' Jake Tapper reports.
Obama will be off the campaign trail Thursday and in Washington to meet with more superdelegates in hopes of swaying them toward his campaign.
The Clinton campaign is also facing signficant money woes.
Clinton has lent her campaign more than $11 million so far this year and the campaign's finances are in rougher shape than previously reported.
"The finance reports show the campaign was carrying a debt of $10 million to $15 million. My sources tell me it's far higher. It could be double that, maybe even more," Stephanopoulos said on "GMA".
Financial debt could be a factor as Clinton weighs her options for continuing what is now seen as a longshot bid for the nomination, though she is favored in the next primary contest in West Virginia.