Mr. Biden did slightly better than Mr. Dodd, but came in fifth.

The candidacy of Gov. Bill Richardson of New Mexico seemed imperiled as well; he came in fourth with only 2 percent of the delegate count.

Every four years, underdogs and underfinanced candidates hope the Iowa caucuses will catapult them from obscurity to the White House, the way they elevated Jimmy Carter in 1976. But the Iowa caucuses have knocked down far more candidates than they have lifted up, and the rules of the Democratic caucuses make it harder for long shots. Candidates who fail to get 15 percent of the delegate count at a precinct are deemed not viable there, and their supporters are invited to throw their support behind other candidates.

Image Credit... Jeff Chiu/Associated Press

In the end, after all the greasy food at the Iowa State Fair, the bus tours through miles and miles of cornfields, the paeans to ethanol, the coffees and town-hall-style meetings, most of the candidates were left with little to show.

On the Republican side, the caucus hurt Mitt Romney, who was the front-runner until about a month ago but who finished second, and Rudolph W. Giuliani, who did not fully compete in Iowa but who appeared to be headed for an even lower-than-expected finish in sixth place, behind Representative Ron Paul of Texas, with three-quarters of the precincts reporting. And Duncan Hunter, a congressman from California, hardly registered at all.