On Tuesday, by contrast, Obama invited every lawmaker who voted for the bill, requiring two events to address all those who wanted to take part after a forecast of rain moved the ceremony from the South Lawn. After the East Room event, Obama and Biden delivered similar remarks to a larger audience in the Interior Department auditorium.

"Everything has the potential these days of being a big event, and if you don't take advantage of it, there's a little bit of a sense of 'What's wrong with you?' " said Stephen Hess, a senior fellow at the Brookings Institution. "It's there to be taken advantage of, which, of course, is the way a White House staff looks at anything."

Bad feelings forgotten

Obama has seen his popularity slide over his year-long push for health-care reform, which Republican critics say has come at the expense of an effective job-creation agenda. His own party split over the scope and cost of the legislation, and the messy process revived a traditional distrust between the House and the Senate, which must still approve a set of House amendments.

But Obama brought them all into one room, where they snapped photographs of one another in front of the podium and touched the desk where the president signed the thick bill. Political enemies became friends again.

Liberal Sen. Al Franken (D-Minn.) mingled among colleagues, at one point leaning over to shake hands with Rep. Bart Stupak (D-Mich.), the antiabortion lawmaker who nearly scuttled the bill. After a few seconds of conversation, Stupak tilted his head back and let out a loud laugh, the months of friction forgotten for a moment.

The 15-foot-tall wooden doors behind the podium slid open around 11:30 a.m., offering a glimpse down a long, column-lined corridor of a portrait of President Bill Clinton on a distant wall. Obama and Biden, each in a navy-blue suit, white shirt and navy-blue tie, entered to applause and chants of "Fired up, ready to go!" from lawmakers, some of whom had questioned the president's commitment, tactics and policy goals over the past year.

In his speech, Obama thanked the lawmakers for their "historic leadership and uncommon courage" during a year of fierce opposition, acknowledging that they had "taken their lumps during this difficult debate."

"Yes, we did," shouted Rep. Gary L. Ackerman (D-N.Y.), drawing laughter from his colleagues with his play on Obama's campaign slogan.

"Our children and our grandchildren, they're going to grow up knowing that a man named Barack Obama put the final girder in the framework for a social network in this country to provide the single most important element of what people need -- and that is access to good health," Biden said in a brief introduction that included the word "history" or "historic" a dozen times.

In the audience was the sister of Natoma Canfield, an Ohio woman and cancer patient who chose her house over health insurance and is now in the hospital wondering how she will pay the bills. Also there was Vicki Kennedy, the widow of Edward M. Kennedy (D-Mass.), a man who for decades worked in the Senate for universal health care.

And so was 11-year-old Marcelas Owens, whose mother died, Obama said, because she was not insured and so could not afford treatment. In a dress shirt, vest and tie, Owens, at the same height as the seated president, leaned over the desk from Obama's right to watch him sign the bill.

A minute or so later, Obama lifted the last of the pens from the desk.

"We are done," he said.

Research editor Alice Crites contributed to this report.