Former UN ambassador Bill Richardson ended his presidential bid Thursday after placing a disappointing fourth in the two opening contests of the Democratic Party's nomination battle.
Richardson, 60, did not immediately endorse any of his Democratic rivals, but urged them to avoid personal attacks on each other as they seek to retake the White House from the Republicans in the November 4 election.
"I gave this race the best I had," said the New Mexico governor, who made the announcement in his home state.
Richardson served as energy secretary and US ambassador to the United Nations under former president Bill Clinton.
He raised more than 22 million dollars for his campaign, but never seriously challenged Hillary Clinton, Barack Obama and former US senator John Edwards in last week's Iowa caucuses and Tuesday's New Hampshire primary.
"They're all strong contenders who each in their own way would bring desperately needed change to our country," Richardson told supporters. "At this time, I will not endorse any candidate." ( Dpa )