The charismatic former president wasn't on stage with Obama early on Wednesday in Chicago, and wasn't even mentioned in the president's victory speech.
But Obama owed Clinton big for a bravura performance on the campaign trail, using his lip-biting charm and mastery of policy to persuade voters in some of the toughest US states that Obama's "got the better argument."
Clinton, as popular now as when he was inaugurated in 1993, retains a hold over US voters and was especially valuable in reaching working-class whites in key states like Ohio and Pennsylvania that were a tough sell for Obama.
"If you vote your hopes and not your fears, if you vote for unity and not division, if you think we can all work together, you will all re-elect Barack Obama President of the United States," the snowy-haired Clinton told a Monday night rally in Pittsburgh, Pennsylvania.
That message apparently carried the day Tuesday when voters re-elected Obama over Republican challenger Mitt Romney by substantial margins even in swing states that had appeared too close to call on election day.
Tuesday night, after receiving a call from Romney conceding defeat, Obama got on the phone and made his first call to Clinton, a campaign official told AFP.
Their remarkable political reconciliation unites two once bitter rivals who as a team of temperamental opposites could give new energy and direction to Obama's second term, at a time when the country faces huge - and divisive - economic challenges.
If the partnership holds, it might also pave the way for another Clinton in 2016.
Hillary Clinton, who is expected to step down as secretary of state, has said she is not thinking about another run for the presidency, but her husband isn't so sure.
"I have no earthly idea what she will decide to do," Clinton said in an interview with CBS in September. "I think we ought to give her a chance to organize her life and decide what she wants to do."
Another potential complication: Vice President Joe Biden's political ambitions.
Asked by a pool reporter after he voted in his home state of Delaware Tuesday whether this would be the last time he voted for himself, the 69-year-old Biden grinned.
"No, I don't think so," he said.
Clashing presidential ambitions were at the root of the Obama-Clinton rivalry, which pitted an upstart one-term Illinois senator against two towering figures in Democratic politics.
The former president was almost contemptuously dismissive of Obama when he defeated Hillary in a fierce fight for the Democratic presidential nomination in 2008. Clinton called Obama's victory a "fairy tale."
But as president, Obama invited Hillary onto his "team of rivals" as secretary of state, a generous gesture that at once held the power couple in check and left the door open to a more genuine reconciliation.
Still, it wasn't until this September, with the president under fire for a flagging economy and high unemployment, that Clinton fully embraced Obama in a speech at the Democratic nominating convention, laying out with logic and conviction why Americans should vote for him.
Even Obama, who turned in a lackluster nominating speech himself, acknowledged that Clinton had made the case for re-election better than he had.
And Clinton lit up the hustings for Obama, his white mane, animated face and folksy turns of phrases captivating undecided voters, many of whom could still remember the era of peace and economic prosperity during his 1993-2001 presidency.
"You have to admire the Clintons. Bill and Hillary Clinton have done more to re-elect Barack Obama than Barack Obama has," marveled former House speaker Newt Gingrich on Fox News.
White House aides spoke of a bond between the two men that grew during the final days of the campaign when a raspy-voiced Clinton joined Obama in one last push for votes.
"I have given my voice in the service of my president," Clinton told a huge Obama crowd in Concord, New Hampshire as the campaign came to a close.