Barack Hussein Obama, a freshman senator who defeated the first family of Democratic Party politics with a call for a fundamentally new course in politics, was nominated by his party on Wednesday to be the 44th president of the United States.
The unanimous vote made Mr. Obama the first African-American to become a major party nominee for president. It brought to an end an often-bitter two-year political struggle for the nomination with Senator Hillary Rodham Clinton of New York, who, standing on a packed convention floor electric with anticipation, moved to halt the roll call in progress so that the convention could nominate Mr. Obama by acclamation. That it did with a succession of loud roars, followed by a swirl of dancing, embracing, high-fiving and chants of “Yes, we can.”
In an effort to fully ease the lingering animosity from the primary season, former President Bill Clinton, in a speech that had been anxiously awaited by Mr. Obama’s aides given the uncomfortable relations between the two men, offered an enthusiastic and unstinting endorsement of Mr. Obama’s credentials to be president. Mr. Clinton’s message, like the messenger, was greeted rapturously in the hall.
“Last night Hillary told us in no uncertain terms that she is going to do everything she can to elect Barack Obama,” Mr. Clinton said. “That makes two of us.”
Mr. Clinton proceeded to do precisely what Mr. Obama’s campaign was looking for him to do: attest to Mr. Obama’s readiness to be president, after a campaign largely based on Mrs. Clinton’s contention that he was not.
“I say to you: Barack Obama is ready to lead America and restore American leadership in the world,” Mr. Clinton said. “Barack Obama is ready to preserve, protect and defend the Constitution of the United States. Barack Obama is ready to be president of the United States.”
Senator Joseph R. Biden Jr. of Delaware, Mr. Obama’s choice for vice president, accepted the nomination with a speech in which he spoke frequently, and earnestly, of his blue-collar background, in effect offering himself as a validator for Mr. Obama among some voters who have been reluctant to embrace the Democratic presidential nominee.
He then turned to Senator John McCain, the likely Republican nominee, signaling how he would go after him in the campaign ahead. He referred to Mr. McCain as a friend — “I know you hear that phrase a lot in politics; I mean it,” he said — and then proceeded to offer a long and systematic case about why Mr. McCain should not be president.
“The choice in this election is clear,” Mr. Biden said. “These times require more than a good soldier. They require a wise leader,” he said, a leader who can deliver “the change that everybody knows we need.”
His 21-minute address completed, Mr. Biden was joined on stage by his wife, Jill, who told the crowd they were about to be joined by an unscheduled guest. The crowd exploded as Mr. Obama walked around the corner.
“If I’m not mistaken, Hillary Clinton rocked the house last night,” he said, gazing up at where Mr. and Mrs. Clinton were watching the proceedings and leading the crowd in applause. “And President Clinton reminded us of what it’s like when you have a president who actually puts people first. Thank you.”
The historic nature of the moment quickly gave way to the political imperatives confronting Mr. Obama, who arrived here on Wednesday afternoon and is to accept the nomination Thursday night before a crowd of 75,000 people in a football stadium. After days in which the convention often seemed less about Mr. Obama than about the two families that have dominated Democratic politics for nearly a half-century, the Kennedys and the Clintons, he needed to convince voters that he has solutions to their economic anxieties and to rally his party against the reinvigorated candidacy of Mr. McCain.
The roll-call vote took place in the late afternoon Wednesday — the first time in at least 50 years that Democrats have not scheduled their roll call on prime-time television — as Democrats sought to avoid drawing attention to the lingering resentments between Clinton and Obama delegates. Yet the significance of the vote escaped no one, and sent a charge through the Pepsi Center as a procession of state delegations cast their votes and the hall, slightly empty at the beginning of the vote, became shoulder-to-shoulder with Democrats eager to witness this moment.
As planned, it fell to Mrs. Clinton to put Mr. Obama over the top. He was declared the party’s nominee at 4:47 p.m. Mountain time after Mrs. Clinton, in a light blue suit standing out in a crowd that included almost every elected New York official, moved that the roll call be suspended and that Mr. Obama be declared the party’s nominee by acclamation. The vote was timed to conclude during the network evening news broadcasts.
“With eyes firmly fixed on the future in the spirit of unity, with the goal of victory, with faith in our party and country, let’s declare together in one voice, right here and right now, that Barack Obama is our candidate and he will be our president,” Mrs. Clinton said.
“I move that Senator Barack Obama of Illinois be selected by this convention by acclamation as the nominee of the Democratic Party for president of the United States,” she said.
Speaker Nancy Pelosi of California, standing at the lectern, asked for a second and was greeted by a roar of voices. A louder roar came from the crowd when she asked for support of the motion.
When the voting was cut off, Mr. Obama had received 1,549 votes, compared with 231 for Mrs. Clinton.
The hall pulsed when Mr. Clinton strode onto the stage for a performance that became a reminder of why Democrats had considered him a politician with once-in-a-generation skills — and suggested that for Democrats in this hall at least, Mr. Clinton may have survived a primary in which he was repeatedly criticized for the sharp tone he often used against Mr. Obama. Again and again, Mr. Clinton tried to quiet the crowd. Again and again, they ignored him.
“You all sit down, we have to get on with the show,” he said.
Mr. Clinton arguably did a better job than Mrs. Clinton the night before in making the case for Mr. Obama, and pumped up a crowd at a convention that has often seemed listless. He even managed, amid all his praise, to slip in a reference to the reservations he voiced about Mr. Obama back when he was campaigning against him, suggesting that Mr. Biden was just what Mr. Obama needed.
“With Joe Biden’s experience and wisdom, supporting Barack Obama’s proven understanding, instincts and insight, America will have the national security leadership we need,” he said.
And without mentioning Mr. McCain by name, he offered a sharp denunciation of him and the Republicans.
“The Republicans will nominate a good man who served our country heroically and suffered terribly in Vietnam,” he said. “He loves our country every bit as much as we all do. As a senator, he has shown his independence on several issues. But on the two great questions of this election, how to rebuild the American Dream and how to restore America’s leadership in the world, he still embraces the extreme philosophy which has defined his party for more than 25 years.”
“They actually want us to reward them for the last eight years by giving them four more,” he said. “Let’s send them a message that will echo from the Rockies all across America: Thanks, but no thanks.”
For all the good Mr. Clinton might have done for Mr. Obama on Wednesday night it marked the second night in a row that the Clintons had been the face of what was supposed to be Mr. Obama’s convention. But when Mr. Obama walked out from backstage at the end of the night — “Hello, Democrats!” — he left little doubt about who was now the face of the Democratic party.
For Mr. Obama, the nomination — seized from Mrs. Clinton, who just one year ago was viewed as the obvious favorite to win the nomination especially against an opponent with a scant political résumé — was a remarkable achievement in what has been a remarkable ascendance. It was less than four years ago that Mr. Obama, coming off of serving seven years as an Illinois state senator, became a member of the United States Senate. He is 47 years old, the son of a white mother from Kansas and a black father from Kenya.
Mr. Obama’s nomination came 120 years after Frederick Douglass became the first African-American to have his name entered in nomination at a major party convention. Douglass received one vote at the Republican convention in Chicago in 1888.
Making the moment even more striking was the historical nature of Mrs. Clinton’s candidacy. She was the third woman whose name has been entered as a candidate for president at a major party convention. As she moved to end the roll-call vote, some women in the hall could be seen wiping tears from their eyes.
