DENVER — Senator Clinton used her high-profile platform at the Democratic National Convention to deliver her most forceful and urgent plea yet to her supporters to get to work for the presumptive Democratic presidential nominee, Senator Obama, who defeated her in a bitterly fought primary battle earlier this year.

“It is time to take back the country we love and whether you voted for me or you voted for Barack, the time is now to unite as a single party with a single purpose. We are on the same team and none of us can afford to sit on the sidelines. This is a fight for the future and it is a fight we must win together,” Mrs. Clinton declared last night.

“We don’t have a moment to lose or a vote to spare. Nothing less than the fate of our nation and the future of our children hangs in the balance,” she said.

Mrs. Clinton wasted little time in delivering an implicit rebuke to some of her backers who have said publicly that they would at least consider supporting the presumptive Republican nominee, Senator McCain of Arizona.

“No way. No how. No McCain,” Mrs. Clinton said. “Barack Obama is my candidate and he must be our president.”

As Mrs. Clinton spoke, the crowd at Denver’s Pepsi Center fell virtually silent for the first time since the convention opened Monday afternoon. Some delegates cried as the former first lady recounted her experiences on the campaign trail and paid tribute to those Democrats, particularly those women, who faithfully stood behind her.

“To my supporters, to my champions, to my sisterhood of the traveling pantsuits, from the bottom of my heart, thank you,” she said. “Thank you because you never gave in and you never gave up. Together, we made history.”

While Mrs. Clinton’s démarche to her supporters was unequivocal, her speech was light on praise for Mr. Obama. She argued, in essence, that electing a Democrat was far preferable to putting Mr. McCain in the White House. Mr. McCain’s campaign immediately pointed out that Mrs. Clinton said nothing about the first-term senator of Illinois being ready to become commander in chief.

Despite Mrs. Clinton’s animation and apparent sincerity, her speech seemed unlikely to extinguish the central narrative of this convention: the sniping between aggrieved supporters of the former first lady and backers of Mr. Obama who believe she is being a sore loser.

While Mrs. Clinton had a needle to thread last night, so too did the former Virginia governor who delivered the convention’s keynote speech, Mark Warner. Many Democrats wanted him to unleash a verbal fusillade against Mr. McCain, but Mr. Warner is running for the Senate this fall in a campaign where he plans to stress his record of bipartisan compromise as governor. He signaled earlier this week that he was not comfortable skewering Mr. McCain.

From the podium last night, Mr. Warner took some swipes at the presumptive Republican nominee, but didn’t ridicule him the way those in lower-profile speaking slots did.

“John McCain promises more of the same. A plan that would explode the deficit and leave that to our kids,” Mr. Warner said. “He would continue spending $10 billion a month in Iraq. I don’t know about you — that’s just not right. That’s four more years that we just can’t afford.”

Mr. Warner sounded his clarion call for bipartisanship, though he managed to move deftly from that into a thinly veiled slap at Mr. McCain.

“If you ran a company whose only strategy was to tear down the competition, it wouldn’t last very long,” the former Virginia governor said. “If an idea works, it doesn’t matter whether it’s got a ‘D’ or an ‘R’ next to it. This election is not about liberal versus conservative, not about left versus right. It’s about the future versus the past,” he said, apparently referring to Mr. McCain’s ideas or perhaps his age.

“This race is all about the future and that’s why we must elect Barack Obama as our next president,” Mr. Warner said.

Talk of an ongoing rift between Mrs. Clinton’s allies and leaders of Mr. Obama’s campaign was fueled further by blunt criticism of the convention’s opening from political strategists with close ties to the former first lady, James Carville and Paul Begala.

Mr. Carville argued that Democrats wasted the first night of the gathering by devoting too much time to warm-and-fuzzy biographical tributes and not enough to attacks on the record of President Bush.

“Maybe we are going to look better Tuesday, Wednesday, and Thursday. But right now, we’re playing hide the message,” Mr. Carville said Monday night on CNN, where he is a paid consultant. “If this party has a message, it’s done a hell of a job hiding it tonight, I promise you that.”

“Frankly, James seems a little cranky these days,” an adviser to Mr. Obama, Anita Dunn, replied on CNN yesterday.

Mr. Begala opined publicly that the selection of Mr. Warner as keynote speaker may have been a mistake because he was balking at taking tough shots at Mr. McCain.

“This isn’t the Richmond Chamber of Commerce,” Mr. Begala said before Mr. Warner’s speech yesterday, according to the Associated Press.

Well before prime time yesterday, Democratic delegates gave a standing ovation to a fiery, populist speech from an unsuccessful, long-shot candidate for the party’s presidential nomination this year and in 2004, Rep. Dennis Kucinich of Ohio.

“In 2001, the oil companies, the war contractors, and the neocon artists seized the economy and added $4 trillion of unproductive spending to the national debt,” the congressman said.

“We went into Iraq for oil,” Mr. Kucinich declared, making a claim popular with left-wing activists but rarely put forward publicly by Democratic officeholders. He also railed against “speculators” on Wall Street.

As he concluded, Mr. Kucinich waved his arms in the air and shouted as if he was presiding over a tent revival. “Wake up, America! Wake up, America! Wake up, America!” he cried.

Other addresses, however, bore the hallmarks of being reined in by convention organizers. During the primary fight, Mr. Obama and Mrs. Clinton jockeyed to outdo each other in repudiating, denouncing, and demanding renegotiation of the North American Free Trade Agreement and other trade deals.

However, last night, brief speeches by the president of the AFL-CIO, John Sweeney, and by Senator Stabenow of Michigan, whose state has been driven into a long, localized recession by manufacturing job losses, made no direct reference to Nafta or any other trade pact.

Ms. Stabenow said Mr. Obama was convinced American workers could “win if the rules are fair,” but she put the emphasis on the potential benefits of trade and not the purported dangers. “He wants to export our products, not our jobs,” she said.

A Michigan auto parts factory worker who spoke to the convention, Robin Golden, complained that he will be unemployed in two weeks. “My job is being shipped to Mexico,” he said. He blamed “tax breaks for companies that outsource jobs,” but he said not a word about trade agreements

Governor Strickland of Ohio did refer in passing to “stuck-in-the-past trade deals,” but did not dwell on the issue.

In an interview in June with Fortune magazine, Mr. Obama said some of the rhetoric he and other candidates used on trade during the Democratic primary was “overheated.”