Hillary Clinton told an exuberant crowd she wanted Barack Obama to win the White House, saying that even though he dashed her presidential dream he is a better choice to lead America than Republican John McCain.
The speech in Washington was Clinton's first at a rally for Obama since their appearance together in June in Unity, New Hampshire, and follows news that former President Bill Clinton, her husband and one of Obama's toughest critics during the Democratic primary, will speak on the third night of the party's national convention.
The developments were a further sign of a thaw in relations between Mr Obama and the Clintons, potentially easing worries within the party that bad feelings from the gruelling primary battle might erupt at the Denver convention later this month.
"Anyone who voted for me or caucused for me has so much more in common with Senator Obama than Senator McCain," Ms Clinton told her cheering audience in the Las Vegas suburb of Henderson. "Remember who we were fighting for in my campaign."
She said last night that "we may have started on two separate paths, but we are on one journey now".
She pointed to key Democratic issues on which Obama and McCain differed — US Supreme Court nominations and health care reform, for example, as reasons that her supporters should not cross party lines.
On the Republican side, the White House announced that Vice President Dick Cheney — a conservative favourite but a divisive national figure — would address the Republican convention along with President George Bush.
There had been doubts about a speech by Mr Cheney, who has been unpopular with most Americans but may be helpful in shoring up the right-wing of the party for Mr McCain, whose reputation as a maverick has worried many evangelical Christians and other Republican conservatives.