On the second night of its national convention, the Democratic Party introduced two newcomers to the nation to set the themes that John F. Kerry hopes will help him win the White House in 2004.

Teresa Heinz Kerry made a quiet but emotionally strong case for her husband as a "fighter" who knows the human costs of war and will not "mistake stubbornness for strength."

And in his debut on the national stage, Barack Obama, who is apparently on his way to victory in the Illinois Senate race and becoming the third elected African American in that body since Reconstruction, said Kerry would heal the bitter divisions in the country and usher in "a politics of hope."

Obama, 42, electrified the convention hall Tuesday night as he said Americans must not allow partisan politics to divide the country: "I say to them tonight, there's not a liberal America and a conservative America -- there's the United States of America."

Both Heinz Kerry, a native of Mozambique and first-generation immigrant, and Obama, the son of a Kenya-born father and a Kansan mother, used their personal histories to sketch a version of the American dream they said had been badly compromised in the four years President Bush has been in office.

Sen. Edward M. Kennedy (Mass.), who was first elected in 1962, shared the oratorical burden at FleetCenter with the two newcomers, but, to the surprise of many, failed to electrify the partisan audience as he had done so many times before.

But his shortcomings were quickly forgotten as Obama stirred the crowd to repeated standing ovations and Heinz Kerry held it almost breathless with her soft-voiced talk.

The candidate's wife, noted for her spontaneous and often barbed comments, did not shy away from her reputation. "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. My only hope is that, one day soon, women -- who have all earned the right to their opinions -- instead of being labeled opinionated, will be called smart or well-informed."

What Heinz Kerry said thereafter was not controversial, as she followed the instruction for the evening to emphasize hope, unity and -- Kerry's favorite campaign word, strength -- after a Monday night session that contained many barbs at Bush.

"John is a fighter," she said. "He earned his medals the old-fashioned way, by putting his life on the line for his country. And no one will defend the nation more vigorously than he will. . . . But he also knows the importance of getting it right. For him, the names of many friends inscribed in the Vietnam Memorial, that cold stone, testify to the awful toll exacted by leaders who mistake stubbornness for strength."

Even without the "red meat" rhetoric, both speeches were well received in the hall. But the biggest ovation of the night may have gone to former Vermont governor Howard Dean, who fought bitterly with Kerry in the primaries, but Tuesday night pledged to support the man who defeated him.

Despite the enthusiasm in the hall for the night's main speakers, the Kerry campaign learned that Monday night's session, featuring former president Bill Clinton and Sen. Hillary Rodham Clinton (N.Y.), was a bust in the TV ratings. The audience size was down 10 percent from the first night of the Los Angeles convention four years ago.

But the delegates, who praised the Clintons' performance, are too focused on defeating Bush to worry about such matters. Kerry, continuing his slow progress toward the convention, told a crowd in Norfolk that the Sept. 11 commission should be extended for 18 months to assure its recommendations are enacted.

That stand -- like much of the oratory Monday and Tuesday nights -- appeared to be designed to underline the contention that Kerry will be as committed to protecting the country as anyone could wish.

Kennedy, who normally can be counted on to energize any Democratic gathering, delivered a speech that was clearly not going to replace his "dream will not die" oration at the 1980 convention.

But Obama made up for the veteran's shortcomings with an address that built in pace and power as it went on. When he reached his climax, the convention crowd was on its feet, cheering every phrase.

Adriana Martinez, a delegate from Las Vegas, said Obama was extraordinary. "Look at the energy he brought to this room," Martinez, 40, said a few minutes after Obama finished. "He is definitely a rising star."

Obama implored the crowd to focus on those who need help most. "We are connected as one people," he said. "If there's a child on the South Side of Chicago who can't read, that matters to me, even if it's not my child. If there's a senior citizen somewhere who can't pay for her prescription and has to choose between medicine and the rent, that makes my life poorer, even if it's not my grandmother.

"If there's an Arab American family being rounded up without benefit of an attorney or due process, that threatens my civil liberties. It's that fundamental belief -- I am my brother's keeper, I am my sister's keeper -- that makes this country work."

Kennedy, who relished the home-city setting of the convention he lobbied long and hard to bring to Boston, condemned the Bush administration for being deliberately divisive. "We have seen how they rule -- they divide and try to conquer. They know the power of the people is weakened when our house is divided. They believe they can't win unless the rest of us lose.

"America needs a genuine uniter, not a divider who only claims to be a uniter," the senator said, praising his junior colleague as the man who can fill that role.

But for once, Kennedy's effort fell flat in the hall. Jerrauld Jones, a former Virginia state delegate, said Kennedy seemed older and ready to move off center stage. "I've never seen him look more like his father than he did tonight," Jones said. "To some extent, it's the passing of the Kennedy mantle to Kerry tonight."

Obama, making his debut in a national forum, had no such difficulties. He was cheered when he contrasted Kerry's style with that of "the spin masters and negative-ad peddlers who embrace the politics of anything goes." In trying to rebut the Bush campaign's contention that Kerry and the Democrats operate on a different values system than the millions of Americans who call themselves conservatives, Obama criticized the journalistic shorthand of red states (Republican) and blue states (Democratic).

"I've got news for them, too," he said. "We worship an awesome God in the blue states, and we don't like federal agents poking around our libraries in the red states. We coach Little League in the blue states and have gay friends in the red states. There are patriots who opposed the war and patriots who supported it. We are one people, all of us pledging allegiance to the Stars and Stripes, all of us defending the United States of America."

The emphasis on unity and optimism was part of the deliberate effort by the Kerry script writers to soften the edges of the partisan rhetoric that dominated the convention's opening session Monday.

It carried over to the speech of Heinz Kerry, famous on the campaign trail for her outspokenness. After describing her husband's service in Vietnam, she switched to such longtime causes of hers as the environment and world peace.

"With John Kerry as president," she said, "global climate change and other threats to the health of our planet will begin to be reversed. With John Kerry as president, the alliances that bind the community of nations and that truly make our country and the world a safer place, will be strengthened once more."

But there were still some serious shots taken. Kennedy brought up "the excesses of Enron" and the "abuses of Halliburton," the energy firm formerly run by Vice President Cheney. When Kerry wins, he said, Cheney will "be retired to an undisclosed location."

Obama, a state senator from Chicago who easily captured the Democratic Senate nomination in his first bid for statewide office and now finds himself without a Republican opponent for an open Republican seat, wove his personal biography into an invocation of the American dream. The honors graduate of Harvard Law School said that "in no other country on Earth is my story even possible."

He talked about the problems Illinoisans face with job losses, rising health care costs and unaffordable tuition, but moved quickly to add that government has only a limited ability to meet these needs. His constituents "don't expect government to solve all their problems," Obama said. "They know they have to work hard to get ahead, and they want to. Go into the collar counties [suburbs] around Chicago, and people will tell you they don't want their tax money wasted by a welfare agency or the Pentagon."

Wading into a controversy in the African American community opened by recent speeches by Bill Cosby, Obama added, "Go into any inner-city neighborhood and folks will tell you that government alone can't teach kids to learn. They know that parents have to parent, that children can't achieve unless we raise their expectations and turn off the television sets and eradicate the slander that says a black youth with a book is acting white."

Obama said, "John Kerry believes in an America where hard work is rewarded." Repeating a theme often voiced here this week, he said Kerry believes that "in a dangerous world, war must be an option, but it should never be the first option."

"We have real enemies in the world," he said. "These enemies must be found. They must be pursued and they must be defeated. John Kerry knows this. And just as Lieutenant Kerry did not hesitate to risk his life to protect the men who served with him in Vietnam, President Kerry will not hesitate one moment to use our military might to keep America safe and secure."

But his theme, like Kennedy's, was heavy on unity -- and the optimism the Democratic ticket is determined to project. "In the end," Obama said, "that's what this election is about. Do we participate in a politics of cynicism or a politics of hope? John Kerry calls on us to hope."

The unity theme was supported by a speaker whose name resonated with any Republicans who tuned in to watch the opposition -- Ron Reagan, son of the late president. He said at the outset, "I am not here to make a political speech, and the topic at hand should not -- must not -- have anything to do with partisanship."

He launched into an emotional plea for accelerated embryonic stem cell research, a cause his mother, Nancy Reagan, has championed since Alzheimer's disease was diagnosed in her husband.

Bush has limited government-financed research to the stem cell lines already in laboratories when he announced his policy in the summer of 2001. Bush said he based his decision on his aversion to seeing fetuses with the potential of life destroyed to harvest more stem cells. But Reagan said that "no fetal tissue is involved in the process, no fetuses are created, none destroyed." In an apparent reference to Bush, someone he has criticized in other settings, Reagan said many opponents of the research are "well-meaning and sincere," but "a few of these folks are just grinding a political ax and they should be ashamed of themselves."

Reagan said the Nov. 2 election poses a choice "between reason and ignorance, between true compassion and mere ideology. Whatever else you do," he said, "I urge you, please, cast a vote for embryonic stem cell research."

At the other end of the political spectrum, Dean endorsed Kerry in a speech that repeated many of the favorite lines of his unsuccessful campaign for the nomination. Reprising the slogan he used then, Dean said, "Tonight, we're all here to represent the Democratic wing of the Democratic Party." His appearance set off a prolonged and enthusiastic standing ovation.

Rep. Richard A. Gephardt (Mo.), another of the losers in the Iowa caucuses that started Kerry on his way, said Kerry would "turn around an economy that has lost a million jobs" since Bush became president.

At an afternoon rally with about 400 people, documentary maker Michael Moore, whose film "Fahrenheit 9/11" has been embraced by the antiwar movement, defended Kerry's vote for authorizing the use of force in Iraq. Saying he had relied on Bush's statements about weapons of mass destruction, Moore said, "If you can't believe what comes out of the mouth of the president of the United States, what are we left with?"

Staff writers Robert G. Kaiser, Howard Kurtz, Michael Shear and Tim Craig and political researcher Brian Faler contributed to this report.

"There's not a liberal America and a conservative America -- there's the United States of America," newcomer Barack Obama said. Teresa Heinz Kerry made a quiet but emotionally strong case for her husband as a "fighter" who knows the human costs of war. "We have seen how they rule -- they divide and try to conquer. They know the power of the people is weakened when our house is divided," Sen. Edward M. Kennedy said of Republicans. Rep. Richard A. Gephardt (Mo.) said that under President Bush, America has lost a million jobs, then said John F. Kerry would turn around the economy. Sandra Maynard listens to Senate hopeful Barack Obama address the convention. Obama drew several standing ovations. Ron Reagan, son of the late president, made a plea for stem cell research. Delegate Edward Lackey, 90, of Ormond Beach, Fla., sports innovative headgear as he observes the convention scene at FleetCenter.