"There are three things that we've seen in past primary elections here. New Hampshire voters don't like front-runners, they don't like establishment candidates, and they don't like the out-of-town pundits telling us who is going to win the primary.
"Most voters haven't decided, so nobody should take the latest polling numbers to the bank on how New Hampshire would vote," he said.
What Democratic insiders are closely watching right now is any sign that Clinton is in danger of falling behind in Iowa and thus stumbling -- as Howard Dean did in 2004 -- just before the pivotal New Hampshire primary.
"You can't say (the nomination is) locked down. We are four lifetimes away from the first ballots being cast by caucus-goers showing up on a cold winter night in Iowa," said Democrat Bud Jackson, a campaign media consultant who is not working for any of his party's contenders.
"She has run a flawless campaign and so far hasn't had any major scandals. But if she stumbles in Iowa, anything can happen," Jackson said.
What could undermine her campaign? Jackson points to troubling news stories last month in the Los Angeles Times that found large donors to the Clinton campaign from New York's Chinese-American community who have no known address and little income.
"Should she slip up, it would remind people of the negative aspects that have historically surrounded her, and her electability would then come into question," Jackson told me.
Until now, Clinton has had an easy ride in the pre-primary season, with her closest rival, Obama, avoiding any direct attacks on her candidacy. But that period has ended, and he has begun to take the gloves off. His polling numbers are inching up in Iowa, and he has begun running TV ads in New Hampshire in the past few weeks that have gotten much more aggressive on Clinton's record.
In sports, they say, "It ain't over 'til the fat lady sings." Clinton's bid for the Democratic presidential nomination may look like a sure thing now. But it isn't over until she shows she can survive the offensive that is shaping up against her in Iowa and New Hampshire.