Any skepticism about reaching broad consensus was vindicated as soon as the first Republican spoke in opposition to the mammoth bills that have passed the House and Senate. Lamar Alexander, of Tennessee, said Congress and the administration should start over and take small steps, including medical malpractice reform, high-risk insurance pools, a way to allow Americans to shop out of state for lower-cost plans, and an expansion of health savings accounts.

"We believe we have a better idea," Alexander said. "Our views represent the views of a great number of American people."  Disagreements were not always expressed diplomatically.  Alexander challenged Obama's claim that insurance premiums would fall under the Democratic legislation. "You're wrong," he said.

Responded Obama: "I'm pretty certain I'm not wrong." As with much in the complicated health care debate, both sides had a point. The Congressional Budget Office says average premiums for people buying insurance individually would be 10 to 13 percent higher in 2016 under the Senate legislation, as Alexander said. But the policies would cover more medical services, and around half of people could get government subsidies to defray the extra costs.

Obama and his 2008 GOP opponent for the presidency, Sen. John McCain of Arizona, had a barbed exchange. McCain complained at length about what he said was a backdoor process to produce the original bills that resulted in favors for special interests and carve-outs for certain states.  "We're not campaigning anymore. The election's over," responded a clearly irritated Obama.  "I'm reminded of that every day," McCain shot back, adding that "the American people care about what we did and how we did it."

Said Obama: "We can have a debate about process or we can have a debate about how we're actually going to help the American people at this point. And I think that's -- the latter debate is the one that they care about a little bit more."

"Not only are lawmakers polarized, the parties' constituencies are far apart," said Robert Blendon, a Harvard University professor who follows public opinion trends on health care. "The president is going to use it as a launching pad for what will be the last effort to get a big bill passed. He will say that he tried to get a bipartisan compromise and it wasn't possible."

The Blair House setting wasn't grand, or even particularly comfortable. About 40 senators, representatives and administration officials were crowded shoulder-to-shoulder around a hollow square table, perched for the six-hour marathon on wooden chairs with thin cushions. Coffee breaks were ruled out, so the only pause in the action came during lunch.

C-SPAN carried complete coverage, while news operations from cable networks to public broadcasting were making it the focus of their day.

Leaving the site during a lunch break, Obama was asked by waiting reporters if he thought the debate was engendering a lot of interest across the country. "I don't know if it's interesting watching it on TV," he responded.