House Majority Whip Rep. James Clyburn of South Carolina went public with his support for Obama, calling the Illinois senator "our nation's best hope for much needed change."
Four other superdelegates quickly followed Clyburn's lead and others, including many members of Congress, are simply waiting, out of respect for Clinton, for the primaries to end to break their silence and endorse Obama.
The next crucial step for the Democrats will be to smooth over the differences between the Obama and Clinton camps so the winner can take on Sen. John McCain, R-Ariz., the presumptive Republican nominee, in the fall.
Obama said Monday that when he talked to Clinton after her Sunday win in Puerto Rico's primary he told her that once the dust had settled, he was looking forward to meeting her at a time and place of her choosing.
There were some bittersweet moments for the Clintons as the campaign came to a close.
An ABC News camera caught Hillary and Bill Clinton in a tender moment on the plane home Monday night that seemed to sum up the grueling campaign. The former president tenderly put his hand on his wife's cheek and then her shoulder, and she responded with a yawn that appeared to drain her whole body.
In what may be one of the last speeches of her campaign, Clinton told a crowd of supporters in Sioux Falls, S.D., "I could not be standing here asking for your support tomorrow without having been the beneficiary of the sacrifice of my family, but of generations of Americans before. … I want to be sure that that dream stays alive."
Bill Clinton was wistful, saying, "This may be the last day I'm ever involved in a campaign of this kind."
But at another point he lashed out bitterly at what he called "the national media's attempt to nail Hillary for Obama... It's just the most biased press coverage in history. … That's what they do -- he gets other people to slime her."
Some Clinton supporters aren't ready to call it quits.
The group Women Count, a PAC of female Clinton supporters, has a new ad running in The Hill and Roll Call newspapers aimed squarely at superdelegates.
"You're still not listening. Our votes are our voices," read the top headline. There is a photo of Clinton and bullet points with her arguments about winning the popular vote, and being the stronger candidate in a general election.
At the bottom of the page it reads: "Superdelegates, look at the facts. The voters have spoken. And remember this is not about you. It's about us."
Stephanopoulos said there is still some pressure for a "dream ticket" of Obama and Clinton, but he reported there is a "lot of resistance in the Obama campaign."
ABC's Sunlen Miller contributed to this report