(AP) - Ailing and aging, Sen. Edward M. Kennedy issued a ringing summons to fellow Democrats to rally behind Barack Obama's pioneering quest for the White House Monday night in a poignant opening to a party convention in search of unity for the fallcampaign.

"Barack will finally bring the change we need," seconded Obama's wife, Michelle, casting her husband - bidding to become the first black president - as a leader with classic American values.

She pledged he would end the war in Iraq, revise a sputtering economy and extend health care to all.

Democrats opened their four-day convention in the shadow of the Rocky Mountains as polls underscored the closeness of the race with Republican John McCain. And there was no underestimating the challenges confronting Obama.

He faces lingering divisions from a fierce battle with Hillary Rodham Clinton for the nomination, tough ads by McCain and his Republican allies, and a reminder that racism, too, could play a role.

"There are people who are not going to vote for him because he's black," said James Hoffa, president of the Teamsters union. "And we've got to hope that we can educate people to put aside their racism and to put their own interests No. 1." He spoke in an Associated Press interview.

Kennedy and Obama's wife were the bookends of an evening that left the delegates cheering, one representing the party's past, the other its present.

"The work begins anew, the hope rises again and the dream lives on," Kennedy said in a strong voice, reprising the final line of a memorable 1980 speech that brought a different convention to its feet. The senator has been undergoing treatment for a malignant brain tumor.

Obama's wife said it was time to "stop doubting and start dreaming."

Moments later, Obama appeared via satellite from Missouri, drawing cheers from delegates.

Convention planners hoped the prime time address by Obama's wife would begin the work of casting the Illinois senator as a leader with classic American values.

Among them, she said: "that you work hard for what you want in life, that your word is your bond and you do what you say you're going to do, that you treat people with dignity and respect, even if you don't know them, and even if you don't agree with them."

The convention's opening gavel fell with Obama and Clinton still struggling to work out the choreography for the formal roll call of the states that will make him the party nominee.

Michelle Obama included a tribute to her husband's former rival, crediting her with having placed "18 million cracks in the glass ceiling" that constrains women's ambitions.