Democratic Party leaders presented a united front behind the presidential bid of their standard-bearer Sen. John F. Kerry on Tuesday and offered voters a platform that excoriates the Bush administration on issues ranging from national security to stem cell research.

Former Vermont governor Howard Dean, who mobilized thousands in an ultimately unsuccessful bid for the Democratic nomination in this year's primaries, received a prolonged ovation as he took the stage on the second night of the Democratic National Convention here to the strains of "Revolution" by the Beatles.

He was followed to the podium by Barack Obama, the convention's 42-year-old keynote speaker, and Teresa Heinz Kerry, the wife of the candidate. Now a state senator in Illinois, Obama is a candidate for the U.S. Senate from that state and is a rising star in the Democratic Party.

A naturalized U.S. citizen who grew up in Mozambique and was formerly married to a wealthy Republican senator from Pennsylvania, Heinz Kerry greeted the audience in Spanish, French, Italian and Portuguese, inviting immigrants like herself to participate in the political process.

She spoke of her life under dictatorship in Mozambique and apartheid in South Africa, where she studied and protested.

"I have a very personal feeling about how special America is, and I know how precious freedom is," Heinz Kerry said. "My right to speak my mind, to have a voice, to be what some have called 'opinionated,' is a right I deeply and profoundly cherish. And my only hope is that one day soon, women who have all earned their right to their opinions, instead of being called opinionated, will be called smart and well-informed, just like men."

Wearing bright red and facing a sea of red signs that said, "We Love Teresa," Heinz Kerry then extolled her husband of nine years.

"John believes in a bright future," she said. "With John Kerry as president, we can, and we will, protect our nation's security without sacrificing our civil liberties. In short, John believes we can, and we must, lead in the world as America, unique among nations, always should--by showing the face, not of our fears, but of our hopes."

In his address to the convention earlier, Dean said, "I was hoping for a reception like this. I was just kind of hoping that it would be on Thursday night, instead of on Tuesday night." Thursday is when the party formally nominates Kerry, 60, a four-term senator from Massachusetts, to challenge President Bush in the Nov. 2 election. Sen. John Edwards of North Carolina, 51, is to be nominated as the vice presidential nominee on Wednesday.

"I may not be the nominee, but I can tell you this: For the next hundred days, I'll be doing everything that I can to make sure that John Kerry and John Edwards take this country back for the people who built it," said Dean. "Because tonight, we are all here to represent the Democratic wing of the Democratic Party."

Dean, who had sharply criticized Kerry during the primaries, told the crowd, "I'm Howard Dean, and I'm voting for John Kerry."

Dean vowed, "We're not going to let those who disagree with us shout us down under a banner of false patriotism. We are not going to give up a single voter, or a single state, because we're going to be proud to call ourselves Democrats, not just here in Boston. We're going to be proud to call ourselves Democrats in Mississippi. We're going to be proud to call ourselves Democrats in Utah and Idaho. And we are going to be proud to call ourselves Democrats in Texas!"

As the crowd applauded and chanted Dean's name, he continued: "Never again will we ever be ashamed to call ourselves Democrats. Never. Never. Never. We're not just going to change presidents, we're going to change this country and reclaim the American dream in this election."

Preceding Dean were two other erstwhile Democratic contenders: Richard A. Gephardt, a former congressman from Missouri, and Carol Moseley Braun, a former senator from Illinois.

Obama described his heritage as the son of a Kenyan man, who grew up herding goats and won a scholarship to study in the United States, and a white woman from Kansas, both now deceased.

"I stand here today, grateful for the diversity of my heritage," said Obama. "I stand here knowing that my story is part of the larger American story, that I owe a debt to all of those who came before me, and that, in no other country on earth, is my story even possible."

Without mentioning anyone by name, he said, "Even as we speak, there are those who are preparing to divide us, the spin masters and negative ad peddlers who embrace the politics of anything goes. Well, I say to them tonight, there is not a liberal America and a conservative America; there is the United States of America. There is not a black America and white America and Latino America and Asian America; there's the United States of America."

Obama asked, "Do we participate in a politics of cynicism or a politics of hope? John Kerry calls on us to hope. John Edwards calls on us to hope." This hope, he said, is not "blind optimism," but "the hope of slaves sitting around a fire singing freedom songs" and "the hope of a skinny kid with a funny name who believes that America has a place for him, too."

Predicting victory for Kerry and Edwards, Obama said, "the people will rise up in November . . . and out of this long political darkness, a brighter day will come."

Speaking before Dean and Obama, Sen. Edward M. Kennedy of Massachusetts welcomed the party's delegates to his hometown , saying he has never seen an election "more urgent or more important" than this year's presidential vote, a contest that he said essentially offers a choice between fear and hope.

Kennedy charged that President Bush has led the country into a "misguided war" in Iraq and "squandered the enormous goodwill that flowed to America from across the world" after the Sept. 11, 2001, terrorist attacks.

"We need a president who will bind up the nation's wounds," Kennedy said. "We need a president who will be a symbol of respect in a world yearning to be at peace again. We need John Kerry as our president."

Kerry "is a war hero who . . . knows that a true leader inspires hope and vanquishes fear," Kennedy said.

"In the depths of the Depression, Franklin Roosevelt inspired the nation when he said, 'The only thing we have to fear is fear itself,'" Kennedy said. "Today, we say the only thing we have to fear is four more years of George Bush." Kerry, he added, "offers hope, not fear."

Earlier in the day, the party's platform, issued without any dissenting minority reports as in previous years, was approved by acclamation. Entitled "Strong at Home, Respected in the World," the platform outlines the Democrats' plans for fighting terrorism, strengthening the U.S. military, achieving energy independence, improving the economy and reforming health care, among other topics.

It charges that the Bush administration "has walked away from more than a hundred years of American leadership in the world to embrace a new -- and dangerously ineffective -- disregard for the world." It adds, "Time and again, this administration confuses leadership with going it alone and engagement with compromise of principle."

By contrast, the platform report says, Kerry and Edwards "believe in a better, stronger America -- an America that is respected, not just feared, and an America that listens and leads."

Edwards arrived in Boston Tuesday to prepare for a speech he is to deliver to the convention on Wednesday. Kerry is due here Wednesday following campaign stops in Norfolk, Va., and Philadelphia.

Democratic delegates, energized after a rousing speech Monday night by former president Bill Clinton and addresses by other party luminaries, gathered in Boston's tightly secured FleetCenter starting at 4 p.m. Eastern time for an afternoon and evening of speeches by party leaders and other participants.

One of the speakers was Ron Reagan, the 46-year-old son of the late president and Republican icon Ronald Reagan. He talked about stem cell research, which has been limited by the Bush administration. Such research offers potential help for sufferers of Alzheimer's disease, which afflicted former president Reagan.

"Now, there are those who would stand in the way of this remarkable future, who would deny the federal funding so crucial to basic research," Reagan said. "They argue that interfering with the development of even the earliest stage embryo, even one that will never be implanted in a womb and will never develop into an actual fetus, is tantamount to murder. A few of these folks, needless to say, are just grinding a political axe, and they should be ashamed of themselves."

Others are "well-meaning and sincere," but "it does not follow that the theology of a few should be allowed to forestall the health and well-being of the many," Reagan said. "And how can we affirm life if we abandon those whose own lives are so desperately at risk?"

In November, he said, voters will face a choice between more than two candidate and two parties. "We can choose between the future and the past, between reason and ignorance, between true compassion and mere ideology," he said. "Whatever else you do come November 2nd, I urge you, please, cast a vote for embryonic stem cell research."

The Democrats' platform endorses stem cell therapy, saying it "offers hope to more than 100 million Americans who have serious illnesses -- from Alzheimer's to heart disease to juvenile diabetes to Parkinson's." The platform charges that Bush "has put ideology over science, skewing information about everything from women's health to scientific research," and it vows to "reverse his wrongheaded policy."

The platform also blasts the Bush administration's energy policy as "government by big oil, of big oil, and for big oil." The administration, it charges, "let oil industry lobbyists and executives write our nation's energy policy in secret," and Bush's policy "leaves America shackled to foreign oil, dependent, vulnerable and exposed." The U.S. economy, it says, now "depends on oil controlled by some of the world's most repressive regimes." The document does not name any such governments.

The platform calls for "investments to harness the natural world around us -- the sun, wind, water, geothermal and biomass sources, and a rich array of crops -- to create a new generation of affordable energy for the 21st century." Among other measures, it calls for funding and incentives for the development, manufacturing and consumer purchase of vehicles that use hydrogen fuel.

As Kerry rallied with thousands of Virginians in Norfolk Tuesday, his top campaign advisers and strategists in five southern states said in Boston that they believe the Democrat has a fighting chance of winning in the South, even though the region is generally seen as leaning toward the Republicans.

In Virginia, which has not voted for a Democratic candidate since Lyndon B. Johnson's landslide win in 1964, the Kerry campaign credits the popularity of Gov. Mark R. Warner for motivating Democratic voters and giving credibility to Kerry's messages.

Across the south, campaign advisers said that the loss of jobs in rural areas provides an opening for Kerry. Layoffs in textile plants, furniture manufacturers and the tobacco industry during the last four years have left a trail of voters who are disaffected with Bush, they argued.

"There's been tremendous economic dislocation in the South," Kerry pollster Mark Mellman said. "As [southerners] have looked for new leadership, there's Senator Kerry. The bad economy has helped them to sour on Bush."

Top campaign officials in Virginia, North Carolina, Arkansas, Louisiana and Florida also said they believe their states are winnable -- despite polls that show the Democrats trailing in some of those states -- in part because of Kerry's appeal among military veterans.

Staff writer Michael D. Shear contributed to this report.