On the eve of the New Hampshire primary, Senator Barack Obama delivered a message to supporters: "Do not take this race for granted. I know we had a nice boost over the last couple of days, but elections are a funny business."
It was a prescient warning.
Mr. Obama, who arrived here five days ago after a commanding triumph in the Iowa caucuses, had planned to leave New Hampshire on a similar high. But a defeat by Senator Hillary Rodham Clinton here on Tuesday evening startled Mr. Obama and ensured that the fight for the Democratic presidential nomination remained fully engaged.
"We know the battle ahead will be long, but always remember that no matter what obstacles stand in our way, nothing can stand in the way of the power of millions of voices calling for change," Mr. Obama said, speaking at a rally of crestfallen supporters. "We have been told we cannot do this by a chorus of cynics that will only grow louder and more dissonant in the days and weeks to come."
For the last five days here, Mr. Obama made one appeal above all to the legions of voters who turned out at rallies from dawn to dusk to see him: Prove that Iowa was not a fluke. He made that pitch again and again to audiences, which spilled from gymnasiums into side rooms and from opera houses onto snow-covered sidewalks, a tableau of young and old pressed closely together as they cheered his historic candidacy.
In the end, though, it was another historic candidacy -- that of Senator Hillary Rodham Clinton -- that appealed to more voters in New Hampshire, particularly women who broke with Mr. Obama in significant numbers in the closing hours of an accelerated campaign here.