DES MOINES, Iowa - Sen. Barack Obama, bidding to be the first black president in American history, won the Iowa caucuses Thursday night, pushing Sen. Hillary Clinton back to third place in the opening test of the race for the Democratic presidential nomination.

On the Republican side, Mike Huckabee rode a wave of support from evangelical Christians to victory over Mitt Romney.

Obama, 46, told a raucous victory rally his triumph showed that in "big cities and small towns, you came together to say, 'We are one nation, we are one people and our time for change has come.'"

Nearly complete returns showed the first-term senator from Illinois with 38 percent support from Democratic caucus-goers. Former Sen. John Edwards of North Carolina was in second place, relegating Clinton, the former first lady, to a close third.

Sen. Chris Dodd of Connecticut and Sen. Joseph Biden of Delaware dropped out of the Democratic race after poor showings, and Mike Gravel was expected to drop out as well. Rep. Dennis Kucinich of Ohio and New Mexico Gov. Bill Richardson finished well back.

Clinton, a New York senator bidding to become the first female president, congratulated Obama but vowed to continue.