In a widely expected move on Wednesday, the North Carolina senator cleared the way for John Kerry who has swept virtually all of the preliminary Democratic nominating contests.
"Today, I've decided to suspend my campaign for the presidency of the United States," Edwards told a crowd of supporters in a speech in Raleigh.
Edwards, 50, quit the race after failing to halt Kerry's advance in 10 crucial Super Tuesday Democratic election contests.
The senator was the last serious obstacle blocking Kerry from locking up his party's nomination to challenge Republican incumbent George Bush in the November election.
He surprised most political analysts by beating several better-known Democratic rivals, won the primary in his native South Carolina, and racked up strong second-place finishes in contests in Iowa, Wisconsin, and Georgia.
But Edwards was unable to hold his own against the juggernaut Kerry campaign, which steamrolled to continued victories in the vast majority of contests.
It has also amassed an almost insurmountable lead in delegates to this summer's Democratic nominating convention.