"If we are really serious about winning this election, Democrats, then we can't live in fear of losing," Obama said, accusing Clinton of running a "poll-driven campaign," in a speech the Obama camp would later use in several effective television ads against Clinton.
"Change is just a word if you don't have the strength and experience to make it happen. We must nominate a nominee who has been tested and elect a president who is ready to lead on Day One. I know what it's going to take to win," Clinton shot back.
National polls still put Clinton on top, but Obama was showing strength in Iowa, where the first contest in the race would be held.
A month later, Obama picked up the endorsement of Oprah Winfrey and the formidable pair hit the campaign trail in Iowa, New Hampshire and South Carolina.
"Experience in the hallways of government isn't as important to me as experience on the pathway to life. I challenge you to see through those people who try to tell you that experience in politics as usual is more valuable than wisdom outside the walls of Washington, D.C.," Oprah told crowds of enthusiastic supporters, though she did not mention Clinton by name.
The tide appeared to be turning back to Clinton when she picked up the endorsement of The Des Moines Register.
"I've got my groove back," Clinton declared in December 2007, when asked by ABC News' Kate Snow about the state of her campaign during a chaotic -- and memorable -- stop for the Clintons at a Hyvee grocery in Iowa.
The Clinton campaign embarked on the "Every Vote Counts" tour of Iowa, dubbed the "Likeability Tour" by the press corps who had accompanied her for nearly a year already.
In an interview with ABC News' Cynthia McFadden for "Nightline" that same month, the candidate expressed cautious optimism that her campaign had turned the corner.
"I think the campaign is doing very well," Clinton told ABC News. "There's a rhythm to campaigns. I know that. I've been in a lot of them over the course of my life. It's really picking up steam, and that's what I feel."
Sen. Clinton traveled Iowa by bus and helicopter, joined by daughter, Chelsea, and her mother, Dorothy Rodham, at various points, making an explicit appeal to women -- her core group of consistent support throughout the campaign.
"We're going to break the highest glass ceiling, for not just me, but for all girls and women," Clinton told "Nightline." "You know that wonderful old line about women do everything? It's like Ginger Rogers did everything Fred Astaire did, only backwards and in high heels. Well, we just have to go out and do it. There's no point in worrying about it."
On Jan. 3, 2008, Barack Obama won the Iowa caucuses. Clinton had been bested not only by Obama but also -- although narrowly -- by Edwards as well.
"They said this day would never come," Obama said in his victory speech, calling the win a "defining moment in history."
With only five days between Iowa and New Hampshire, Clinton didn't have much time to slow Obama's momentum.
At the ABC News/WMUR/Facebook debate on Jan. 5, 2008, Clinton and Edwards came out strong against Obama.