Dodd, who received less than 1 percent of the vote in Thursday's Iowa caucuses, with 99 percent of precincts reporting, told his supporters via e-mail Thursday night that he is leaving the presidential race.
"I count the past year of campaigning for the presidency as one of the most rewarding in a career of public service. Unfortunately, I am withdrawing from that campaign tonight," Dodd wrote. "But there is no reason to hang our heads this evening -- only the opportunity to look towards a continuation of the work we started last January: ending the Iraq War, restoring the Constitution, and putting a Democrat in the White House. … You've been an invaluable ally in the battle, and I'll need you to stick by my side despite tonight's caucus results."
Biden, meanwhile, said in a speech to supporters that he started his campaign because of his belief in the nation.
"There's no reason not to be happy," he said. "The promise of this nation is immense."
Biden said he plans to remain in the Senate as head of the Foreign Relations Committee.
"I ain't going away, let me make that clear," he said.
The Democrats field is still well populated, with Sen. Barack Obama, D-Ill; Sen. Hillary Clinton, D-N.Y.; former Sen. John Edwards, D-N.C.; New Mexico Gov. Bill Richardson; U.S. Rep. Dennis Kucinich, D-Ohio; and former U.S. Sen. Mike Gravel, D-Alaska.