This story was written by CBSNews.com political reporter David Miller.
Since her third-place finish in the Iowa caucuses, Democrat has tried to project an image of strength, sounding as confident as when she was her party's front-runner, and even getting a little angry when talking about the man who has supplanted her in that spot, .
But it was a simple question that, on Monday, may have shown the intense pressure Clinton is facing in Tuesday's New Hampshire primary is getting to her in the campaign's closing hours. At a café in Portsmouth, the last question from a group of undecided voters came from Marianne Pernold, a freelance photographer who is torn between Clinton and Obama.
"How do you do it?" she asked - curious more about the physical rigors of the campaign than anything else, she said afterward.
But Clinton answered the question in a broader sense, and her emotions revealed themselves - her voice cracked and quavered, her eyes turned watery.
"It's not easy, it's not easy and I couldn't do it if I didn't passionately that it was the right thing to do," she said. "It's not just political. I see what's happening. We have to reverse it. Some people think elections are a game - who's up, who's down. It's about our country. It's about our kids' futures."
The emotion building - as cameras zoomed in and photographers snapped away furiously - Clinton, speaking softly, reiterated what has been her core argument the past four days: readiness.
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"We do it, each one of us, because we care about our country," she said. "Some of us are right and some of us are wrong. Some of us are ready and some of us are not. Some of us know what we will do on day one, and some of us haven't, maybe, thought that through enough."
It would be hard to blame Clinton for cracking - even just a little - given the circumstances she's facing. She has been outflanked by Obama, who has turned his campaign into a movement that has drawn in large numbers of independent and young voters. Her third-place finish in Iowa has made New Hampshire a crucial test. An Obama win here - and polls are predicting just that - could give the Illinois senator even more momentum for Clinton to overcome.
"It's a genuine moment - she's talking about her passion for the country," Clinton spokesman Jay Carson said of the candidate's emotional response. "For her it's about people. That's all it's about for her. That's why she does this."
Right now, however, Clinton's opportunity to be president appears to be slipping away, and her campaign is trying to right the ship while stealing momentum from Obama. But her aides suggest that isn't going to happen in New Hampshire, which they now portray as merely the first part of a lengthy national campaign for the nomination.
"New Hampshire is the 'first in the nation' primary, not the 'first and last in the nation' primary," said Clinton strategist Doug Hattaway. "So, you know, we're working hard to do well in New Hampshire tomorrow, but there's lots of other states to go."
Among those states is South Carolina, which holds its primary Jan. 26. The state is home to a large contingent of black Democrats which could benefit Obama, with his win in Iowa proving to them his viability. After that come nearly two-dozen states on Feb. 5, a day which is widely expected to effectively determine the Democratic nominee.
Clinton held large leads in those states throughout 2007. But a new national survey from Rasmussen Reports suggests that is changing - Clinton's lead over Obama was down to 4 percentage points, equal to the poll's margin of error.
The campaign hopes, however, that the run-up to Feb. 5, and the increased time between contests, will allow people to examine Obama more thoroughly and decide that Clinton is the better choice.
"I think what you'll see is people looking to get though all the talk, because everybody is talking about change," Hattaway said. "And when people look past the talk is when you start to see the distinctions."
But time is running out and the challenge Clinton faces is a tough one. Proof of that might be seen in Marianne Pernold's reaction to seeing the New York senator on the verge of tears, showing the emotion she's often criticized for lacking. She said the moment made her cry, too - but that even though she was now leaning toward voting for Clinton, she was still undecided.
"Obama moved me to tears, too," she said. "I'm smitten by Obama. I'm smitten by him. But Hillary showing that emotion just really - I found that really refreshing."
By David Miller