Howard Dean has formally announced that he is “no longer actively pursuing the presidency”.
He said he would not run as an independent and would back the eventual party nominee.
But he vowed to use his support base to build a new grassroots group which would transform the Democratic party and the nation at large.
He said: “I am no longer actively pursuing the presidency.
“We will, however, continue to build a new organisation using our enormous grassroots network to continue the effort to transform the Democratic party and to change our country.”
He said: “I will not run as an independent or third party candidate. And I urge my supporters not to be tempted by any effort by another candidate.
“The bottom line is that we must beat George W Bush in November whatever it takes.
“I will support the nominee of our party, I will do everything I can to beat George W Bush.”
He said that during his campaign he had “exposed the dangerous radical nature of George W Bush’s agenda”.
And he added: “We have demonstrated to other Democrats that it is a far better strategy to stand against the right-wing agenda of George W Bush than it is to cooperate with it.”