The Democratic presidential race took so many twists that close observers might have needed a chiropractor to follow it. And now Clinton, once the instant favorite in a crowded field of candidates, is struggling to overcome a daunting wave of Obamania.
"There's a problem with inevitability," said Dick Harpootlian, a former South Carolina party chairman who supports Obama. "It rarely proves to be true."
When Clinton joined the race in January 2007 with a cozy Webcast from her living room couch, the notion of a former first lady-turned-senator running to be the first female president was so new, so different, she quickly eclipsed rival candidates such as Joe Biden, Chris Dodd, Bill Richardson, all seasoned politicians with solid credentials.
"I'm in to win," Clinton proclaimed. And she had the money to back up her bravado.
"I don't think anyone can stop her," John Catsimatidis, a New York businessman and member of Clinton's finance team, trumpeted in February 2007. "She's unstoppable; she's got such a machine."
Clinton, intent on keeping 2000 nominee Al Gore out of the race, seemed to regard all other rivals as "Lilliputians," says Democratic pollster Peter Hart
Her Democratic opponents didn't buy it, though, and neither did the public.
"I lived through the inevitability of Howard Dean," scoffed John Edwards, recalling the early darling of the 2004 presidential race who quickly faded from the Democratic field.
But it was Obama, not Edwards, who emerged as the anti-Clinton.
Bidding to become the nation's first black president, Obama offered a fresh new face, and a message of hope and change that captured the public's imagination.
His first visit to New Hampshire, back in December 2006, before he'd entered the race, sparked such a frenzy of interest that even Obama dismissed it as hype, as his 15 minutes of fame.
"I think to some degree I've become a shorthand or a symbol or a stand-in for now," he said. "It's a spirit that says we are looking for different. We want something new."
Obama joined the race in January 2007, a week before Clinton, and soon proved that his appeal with voters was no passing fancy, that he was more than a cardboard stand-in.
He turned his short resume - just two years of national experience as a senator
- into an asset by stressing that it was time for a new generation to step forward.
Obama's surprising ability to raise money - by the boatload - instantly served notice to Clinton that he was not to be discounted.
He matched Clinton almost dollar for dollar in the first three months of 2007, and breezed right past her in the next quarter
- raising $33 million to her $27 million. By year's end, both had raised more than $100 million and blown through at least $80 million, muscular figures that no other Democrat could touch.
"That really changed the whole tenor of the race to becoming more of a two-person contest than a coronation," said Anthony Corrado, a campaign finance expert at Colby College in Maine.
Clinton did her best to maintain the illusion of inevitability nonetheless.
In July, she dismissed Obama as "irresponsible and frankly naive" on foreign policy.
In September, she ran the gantlet of five Sunday talk shows in one day, working in the phrase "When I'm president" at least seven times.
As recently as November, she calmly told an interviewer that despite Obama's surprisingly strong challenge, "it will be me."
Late into the fall, there were plenty of believers in a Clinton juggernaut.
"If this were a wedding, we'd be at the 'speak now or forever hold your peace' part," Steve McMahon, a former Dean adviser, said of Clinton's strength in October.
But soon there were signs of trouble for her.
