With a vow to restore trust to the White House and "never mislead us into war," John F. Kerry accepted the Democratic Party's presidential nomination Thursday night and asserted that "America can do better" than it has during the last four years under President Bush.

After entering the Democratic National Convention hall to wild applause and making his way through the delegates to the strains of the Bruce Springsteen song, "No Surrender," Kerry took the stage and embraced a host of fellow Vietnam veterans, including a former Green Beret whose life he saved and a dozen former crew mates on patrol boats he commanded. Delegates hoisted signs with their candidate's name and chanted, "Kerry, Kerry."

As he stepped to the podium, Kerry immediately departed from his prepared text. "I'm John Kerry, and I'm reporting for duty," he said, snapping a salute to the audience.

In an acceptance speech that mixed biographical details with policy goals and repeated expressions of optimism, the 60-year-old senator from Massachusetts called on voters to help him "write the next great chapter of America's story."

Culminating the Democrats' four-day national convention here, Kerry declared, "We have it in our power to change the world again. But only if we're true to our ideals -- and that starts by telling the truth to the American people. That is my first pledge to you tonight. As president, I will restore trust and credibility to the White House."

He said, "For all those who believe our best days are ahead of us . . . with great faith in the American people, I accept your nomination of president of the United States.

Kerry, speaking after introductory addresses by his daughters and by former senator Max Cleland of Georgia, attempted to draw a sharp contrast between his approach to leadership and that of President Bush, whom he faces in the Nov. 2 election.

"I will be a commander in chief who will never mislead us into war," he said. "I will have a vice president who will not conduct secret meetings with polluters to rewrite our environmental laws. I will have a secretary of defense who will listen to the advice of our military leaders. And I will appoint an attorney general who will uphold the Constitution of the United States."

Yet Kerry also appealed to Bush to join him in being "optimists, not just opponents," and he pledged to appoint Republicans, if he is elected, "so that no one who has something to contribute will be left on the sidelines," according to remarks prepared for delivery.

Even before Kerry spoke, the campaign of Bush and Vice President Cheney said it was bracing for what GOP leaders predicted would be "a significant bounce" in the polls for the ticket of Kerry and his running mate, Sen. John Edwards of North Carolina. The Kerry campaign, seeking to lower expectations, has said repeatedly it was not expecting such a bounce.

The Bush campaign, reaffirming a denunciation of the Democrats' "extreme makeover" at the convention, said Kerry's "well-crafted speech" would leave "gaping holes in a record that earned him great distinction -- as the Senate's most out of the mainstream member."

In the prepared draft of his acceptance speech, Kerry briefly addressed the Republicans' attacks on him as a "flip-flopper" on issues, notably the war in Iraq. Although he voted to authorize the war, he has subsequently criticized it and rejected a Republican bill to fund it in favor of a Democratic alternative.

"I am proud that after September 11th all our people rallied to President Bush's call for unity to meet the danger," Kerry said of the terrorist attacks that claimed the lives of more than 3,000 people nearly three years ago. "There were no Democrats. There were no Republicans. There were only Americans. How we wish it had stayed that way."

According to the prepared remarks, he continued: "Now I know there are those who criticize me for seeing complexities -- and I do -- because some issues just aren't all that simple. Saying there are weapons of mass destruction in Iraq doesn't make it so. Saying we can fight a war on the cheap doesn't make it so. And proclaiming mission accomplished certainly doesn't make it so."

Kerry pledged, "As president, I will ask hard questions and demand hard evidence. I will immediately reform the intelligence system -- so policy is guided by facts, and facts are never distorted by politics. And as president, I will bring back this nation's time-honored tradition: the United States of America never goes to war because we want to, we only go to war because we have to."

Saying that "I know what we have to do in Iraq," Kerry called for building alliances to share the burden, reduce the cost to the United States and lower the risk to U.S. soldiers. But he said that would not happen without new leadership.

"I defended this country as a young man, and I will defend it as president," Kerry said. "To all who serve in our armed forces today, I say, help is on the way. As president, I will fight a smarter, more effective war on terror. . . . In these dangerous days, there is a right way and a wrong way to be strong. Strength is more than tough words. After decades of experience in national security, I know the reach of our power, and I know the power of our ideals."

Calling the Nov. 2 vote "the most important election of our lifetime," Kerry said repeatedly, "America can do better. And help is on the way." The slogans recalled the words of John F. Kennedy during his 1960 election campaign ("we can do better") and the Bush-Cheney campaign slogan of four years ago ("help is on the way").

Kerry spoke after the unveiling of a nine-minute documentary film on Kerry's life that was directed by filmmaker James Moll with advice from renowned director Steven Spielberg. The documentary, narrated by actor Morgan Freeman, features members of Kerry's family and fellow Vietnam veteran Jim Rassman, a Green Beret whom Kerry rescued from a river in Vietnam under enemy fire in March 1969.

Rassman, 57, a retired sheriff's deputy from Oregon who had been a registered Republican for more than 30 years, addressed the convention before his introduction by Cleland, who lost both legs and an arm in Vietnam. Appearing on the stage with Rassman were a dozen of Kerry's former crew mates from two Navy Swift boats he commanded during the war.

The evening had its lighter moments, as well. His daughter, Alexandra Kerry, related what she said was a "silly," but true, story of a July day when she and her sister, Vanessa, were little girls preparing for a boat trip with their father. Vanessa's pet hamster, packed in its cage, fell off the dock, seemingly doomed. But their father jumped into the water, fished out the cage with an oar, "hunched over the soggy hamster and began to administer CPR," Alexandra said, as the audience howled.

"There were some reports of mouth-to-mouth, but, I admit that's probably a trick of memory," she said. "The hamster was never quite right after that, but he lived."

Kerry's speech, widely described as the most important of Kerry's life, was a prime-time address that aides said would seek to convey an image of strong leadership for troubled times.

It came after his running mate, Edwards, was formally nominated by acclamation, a day after he rallied delegates with a generally well-received convention speech in which he promised that "hope is on the way."

Speaking before Kerry Thursday, a stream of Democratic elected officials, union leaders, veterans and civil rights activists promoted the Massachusetts senator's candidacy.

Retired Army Gen. Wesley K. Clark, who competed in this year's early Democratic primaries against Kerry, said, "And this soldier has news for you tonight: Anyone who tells you that one political party has a monopoly on the best defense of our nation is committing a fraud on the American people."

Clark added: "The safety of our country demands an end to the doctrinaire, ineffective policies that currently grip Washington. Enough is enough! A safe America, a just America, that's what we want. That's what we need. And with John Kerry and John Edwards, that is what we will achieve."

Virginia Gov. Mark R. Warner vowed that his state would "prove the pundits wrong" and help elect Kerry in November. "Yes, John Kerry can win in Virginia and across the South," Warner said.

Washington, D.C., Del. Eleanor Holmes Norton, the District's lone, non-voting representative in Congress, stumped for statehood for the jurisdiction of nearly 600,000 people.

"One day the nation's capital will have equal rights to democratic self government as the 51st state," she said. "Until then, right now, no American should be paying taxes without representation."

Kweisi Mfume, the president of the NAACP, said, "We mean it when we say that racism, sexism and anti-Semitism are wrong. We know that black bigotry is just as cruel and as evil as white bigotry. We understand that gay bashing and immigrant bashing and union bashing deplete us as a nation."

Sen. Carl M. Levin (D-Mich.), the top Democrat on the Senate Armed Service Committee, hailed Kerry as a leader who "knows that America is at its strongest and best when we are respected not only for our military power, but also for the wisdom and restraint with which we use it."

He said, "John Kerry understands that if we develop new nuclear weapons, if we walk away from treaties, if we ignore international law, other nations will follow that same dangerous course." And with the election of Kerry, Levin said, U.S. forces serving in Iraq, Afghanistan and elsewhere will have "a commander-in-chief for whom 'leave no American behind' is not a slogan but a solemn personal duty tested and proven under fire."

Kerry went to the FleetCenter shortly before noon to check out the podium from which he will address more than 4,000 convention delegates and a television audience of millions across the nation. Wearing an open-collared shirt and a blue blazer, Kerry tested the teleprompters and the microphone as he briefly went through the motions of delivering his speech.

Kerry had watched on television from his Beacon Hill home late Wednesday as the traditional roll call of state delegations officially gave him the nomination. Shortly before midnight, the delegation from Ohio, one of the key battleground states, put Kerry over the threshold of 2,162 votes needed to make him the nominee.

Kerry campaign officials said that although the three major broadcast television networks have aired relatively little live coverage of the convention so far, the campaign is pleased by the response to the event from Americans using other media.

So far, the convention's Web site has recorded "50 million hits," and Wednesday the campaign received $3 million in donations over the Internet, a one-day record, said Peggy Wilhide, the convention's communications director.

The broadcast TV networks planned an hour of live reports Thursday night starting at 10 p.m. Eastern time to cover Kerry's address.

Hours after his acceptance speech, Kerry and Edwards plan to set off on a coast-to-coast journey dubbed the "Believe in America Tour," traveling west by bus, train, boat and plane to battleground states. Campaign officials said the 3,500-mile trip beginning Friday morning would be reminiscent of the 1948 whistle-stop tour of president Harry S. Truman.

A campaign spokeswoman, Debra DeShong, said Kerry's acceptance speech would "leave people with a sense that in very serious times, he has the strength to move the country forward." She said it would be "a very forceful, optimistic speech laying out his vision for a strong America." Kerry, she predicted, "is going to look presidential."

Asked why the campaign was putting so much emphasis on Kerry's service in the Vietnam War more than three decades ago -- a war that he subsequently opposed -- DeShong told reporters Thursday, "Because that's a tremendous part of who John Kerry is." She said the emphasis was on "service to country that began in Vietnam."

DeShong was also asked how the campaign plans to deal with a GOP strategy aimed in part at preventing Republicans who are disenchanted with President Bush from straying all the way into the Kerry camp by making the Democrat appear unacceptable.

"Part of that starts tonight," DeShong said. "We're going to capture the attention of America, and breaking down that firewall begins tonight in a major way. That comfort level that we need to reach with voters is really going to begin this evening when John Kerry speaks from the heart."

As the preparations proceeded, a small demonstration erupted near the convention site after three days of unexpected calm.

At about 4 p.m., a group of about 200 protesters paraded from Copley Square to the FleetCenter, where they burned a two-headed effigy of Kerry and Bush, Washington Post staff writer Jonathan Finer reported. The protesters, many of whom were opposed to the war in Iraq, jostled with police in riot gear on Canal Street while a police helicopter circled overhead and dozens of journalists watched. There were some minor injuries on both sides in the confrontation. Boston Police Superintendent Robert Dunford said he was "sucker punched" in back of the head but not seriously hurt.

At least two protesters were arrested, one for assaulting a police officer and one for possessing an accelerant. In a nearby area cordoned off for lawful protests, police confiscated wire cutters from protesters who tried to cut through a fence but no arrests were made.

Before this afternoon, only two people had been reported arrested by police guarding the convention site, one a man who was apparently intoxicated and the other a woman who drove through a checkpoint.

The Associated Press reported earlier that about 100 protesters from a group calling itself Critical Mass rode bicycles through the city Thursday as police tried to keep up on their own bikes. It was not immediately clear what the group was protesting.

In addition, a Boston-area group of anarchists called for "decentralized direct action" Thursday.

In one of the state delegations' final breakfast meetings Thursday morning, AFL-CIO President John J. Sweeney told Maryland delegates that organized labor would help defeat a president he called an enemy of workers, Washington Post staff writer Tim Craig reported.

Sweeney, a Maryland delegate from Montgomery County, told state party leaders and activists that he couldn't be happier with Kerry's efforts to reach out to organized labor.

"This week, we now feel we are really a full part of the national Democratic Party because John Kerry has gone out of his way to make it that way," Sweeney told the crowd of 150 Maryland Democrats.

Later he said, "Our current president in the White House is simply the worst president in our history. He is the biggest enemy of our workers and their unions, and we're going to beat that son of Bush."

The appearance was a warm-up for Sweeney, who is scheduled to address the convention at 7:45 p.m. He said he plans to build on Edwards's speech Wednesday night that sought to reach out to working-class voters. Sweeney will be joined on stage by Stephen White, a Silver Spring man who the AFL-CIO says was fired from Comcast recently because he tried to form a union.

Maryland Democratic leaders said Edwards's "hope is on the way" message gives them a powerful tool to use when they get home to try to boost Kerry's candidacy.

Rep. Chris Van Hollen told the delegation that his young son, Alexander, recalled the slogan as the two were stuck in traffic after the session adjourned.

"My son said, 'Don't worry, tomorrow will be a better day because hope is on the way,'" Van Hollen told the crowd. "So you know if my 8-year-old son who was half asleep got it, the rest of America got it."

And while many Democrats have steered cleared of harsh attacks on Bush inside the convention hall, the speakers at the Maryland delegation's breakfast were far less restrained.

"Without question, the Bush administration has failed," said Rep. Albert R. Wynn (D-Md.). "We have a leg up . . . but we got to make sure we go out and beat this chump. We got to win this election."

Soo Lee-Cho, 32, a delegate from Rockville attending her first convention, said she was ready to work for the Democratic ticket. "It has motivated me like never before," she said.

But with most Democrats confident Kerry will win heavily-Democratic Maryland, state activists are planning to work for the Democratic ticket in neighboring states that are expected to be more competitive, including Pennsylvania, West Virginia and Virginia.

The Maryland Young Democrats have announced they are sending 200 of their members to campaign for Kerry in Montgomery County, Pennsylvania, on Sept 11 and 12.

Washington Post staff writer Mark Stencel and washingtonpost.com producer Anne Rittman contributed to this report.