An audience seldom shares the stage with the star. The inauguration of Barack Obama was a rare exception.

On an unparalleled, inspirational American day, Obama offered the country a new, more sober brand of politics. He delivered a call to national service at a time of deep economic distress and extended a generous hand to the rest of the planet.

"The world has changed," the new president declared, "and we must change with it." His remarks were surprisingly detailed and pragmatic for an inaugural address. Shorn of the soaring oratory for which he's become known, they seemed tailored more to coming legislative battles and diplomatic exchanges and less for the ages.

Small matter, in all likelihood, given the extraordinary moment: The day itself - his coming to power before an unprecedented crowd of eyewitnesses - was epochal enough.

Obama took pointed note of the remarkable circumstances, which overshadowed everything else: a celebration of presidential oath-taking by, as he put it, a man "whose father, less than 60 years ago, might not have been served at a local restaurant."

The arrival of the first African-American family in the White House occasioned an outpouring of symbolism and emotion not witnessed in Washington for decades.

More than a million people, by various estimates, jammed the city's monumental core, swept clear of ordinary traffic to enhance security and accommodate their numbers. Students excitedly chanted his name, and elderly black women determinedly pushing walkers together made their way to the chilly, wind-swept National Mall.

Obama could see them over the bulletproof glass of the podium on the Capitol's West Front, a breathtaking, organic mass, spreading westward two miles to the Lincoln Memorial and pulsing with energy. They came alive every time his image appeared on Jumbotron screens, and they turned the Mall a shimmering red as they waved tens of thousands of American flags given away by his inaugural committee.

Those who hung on his words, in person and electronically, attested to the influence of America's new global president. Almost certainly, they made up the largest audience ever to witness an inaugural speech. And thanks to the ever-growing reach of the Internet, more eyes and ears around the world may have caught Obama's message than any previous political leader's.

House Majority Leader Steny H. Hoyer, the Maryland Democrat who helped escort Obama to his seat, said the day "was about far more than one man. It was about the millions who shaped a movement for change and the millions more who came to Washington to take part in history and a new spirit of public service."

But Hoyer added that Obama "will be judged by a single standard: his success in meeting the tremendous challenge of the days and years to come, beginning with two wars overseas and an economic crisis here at home."

That was clearly Obama's focus yesterday.

There were nervous moments when Chief Justice John G. Roberts Jr. muffed the words of the presidential oath, written in the Constitution. And Obama flubbed his place in the presidential line. He isn't the 44th American to take the oath, though he's the 44th president ( Grover Cleveland, who served nonconsecutive terms, gets counted twice).

When Obama lifted his hand from the Lincoln Bible, and accepted a congratulatory handshake from Roberts, it was the ceremonial conclusion to one of the most remarkable transitions in nearly two and a quarter centuries.

Perhaps not since George Washington first recited the words in 1789, or when power peacefully passed a dozen years later to a member of a rival party, Thomas Jefferson, had the mere act of taking office carried such profound significance.

Once, blacks were not considered full human beings by the government, which counted them as three-fifths of a person for census purposes. Now, a biracial American leads that government, in a job that had been the exclusive province of whites.

His Arabic middle name, Hussein, recited in the course of his oath-taking, may have caused millions of American ears to prick up at a time when Islamic extremism is a threat to peace and poses a constant menace to U.S. servicemen and women overseas.

Obama took the unusual step of addressing the world's Muslims. He did so in the context of America's progress in overcoming the burdens of slavery and segregation, portraying that as a hopeful sign that "old hatreds shall someday pass" and "lines of tribe" will dissolve in foreign lands.

"We seek a new way forward, based on mutual interest and mutual respect," he told Islam's 1.5 billion adherents, and issued an ambitious promise to help Third World countries develop more productive farms, clean water and better schools.