IN an extraordinary daylong televised debate, President Barack Obama and Republicans clashed over his plan to overhaul US health care. In the end, there was little reason to hope for a compromise on an issue that could shape Obama's legacy.

The lack of consensus could prompt Democrats to attempt politically risky parliamentary maneuvers to try to get a bill through Congress without any Republican support. That could make health care an even more volatile issue going into the November congressional elections, when Republicans hope Democrats will suffer heavy losses.

Neither side gave ground, despite calls for bipartisanship. Obama implored participants not to merely trade talking points. But that is largely what they - and he - did over 7? hours in Blair House, the presidential guest house across from the White House.

Obama acknowledged agreement may not be possible.

"The truth of the matter is that politically speaking, there may not be any reason for Republicans to want to do anything," Obama said, summing up. "I don't need a poll to know that most Republican voters are opposed to this bill and might be opposed to the kind of compromise we could craft.

"And if we can't," he added, "I think we've got to go ahead and some make decisions, and then that's what elections are for."

It was remarkable political theater. Obama and his top aides, packed around a table with 38 leading lawmakers. They were mostly polite, but ardently exchanged their views with each other and before a television audience of millions.

No participant publicly called the daylong exercise a waste of time. Despite flare-ups now and then, they had a remarkably civil debate on an issue that has divided Americans and polarized political partisans.

There were some areas of agreement, including barring insurers from dropping policyholders who become sick, ending annual and lifetime monetary limits on health insurance benefits and letting young adults stay on their parents' health policies until their mid-20s or so.

Obama acted as both moderator for the meeting and chief advocate for the plan. He was conciliatory at times, testy at others. When a top Republican congressional leader, Eric Cantor, sat in front of a stack of 2,400 pages representing the Senate health care bill, Obama denounced the use of props "that prevent us from having a conversation."

He had a barbed exchange with his former Republican rival, John McCain, who complained that Obama reneged on a campaign promise to bring change to Washington. Obama bluntly told McCain that "we're not campaigning any more. The election is over." McCain retorted that he's "reminded of that every day."

Obama has called for revamping the US health care system to provide coverage to the more 30 million people who are now uninsured. His plan is aimed at making private insurance more affordable and barring companies from excluding high-risk customers, while requiring all Americans to obtain coverage.

Congressional aides said top Democrats will take a few days to gauge the summit's impact on the public and, perhaps more importantly, on moderate House members who will likely determine whether any health care bill will pass.

If the effort fails, Democrats may try a scaled-back plan to insure about 15 million more Americans, rather than 30 million.

Both chambers in the Democratic-controlled Congress had approved separate health bills last year. As they were working out details of a final version of the legislation, Republicans unexpectedly won a Senate seat in a special election in Massachusetts. That cost the Democrats their 60-vote supermajority needed to overcome Republican procedural obstacles.

After the vote, some Democrats were ready to abandon health care as a top issue. Public support was weak and the issue was seen as contributing to the Republican victory. But the White House is making what is seen as one last push before congressional campaigns begin in earnest.

"We cannot have another yearlong debate about this," Obama said at the end of the session.

Thursday's meeting allowed Obama to carry out a 2008 campaign promise to hold health care negotiations in public. He had been criticized for breaking that pledge, with the back-room dealmaking contributing to public wariness of the plan.

Democrats argued at Thursday's meeting that a broad overhaul is vital for America's future. Obama described health care as "one of the biggest drags on our economy."

Republicans denounced the Democratic plan as too costly and intrusive, giving the government control over personal health care choices. They have called on Democrats to scrap their bill and work on a small-scale effort, aimed at cutting costs and eliminating waste and fraud.

Democratic leaders had little illusion that the meeting would win over Republicans at Thursday's meeting. But they hoped to boost support from wavering moderates from their own party. That would be essential if Democrats try to use a controversial procedure known as reconciliation that would allow them to pass the bill with only a simple majority.

Republicans repeatedly warned Democrats not to attempt it, but Obama defended the practice. "I think most Americans think that a majority vote makes sense," he said.

A USA Today/Gallup survey released yesterday found Americans tilt 49-42 percent against Democrats forging ahead by themselves without Republican support. Opposition was even stronger to the idea of Senate Democrats using the special rules, with 52 percent opposed and 39 percent in favor.

Even if they can get health care legislation through the Senate, Democrats are not assured of winning simple majority in the House of Representatives. The health bill passed there last year 220-215, with 39 Democrats opposing it. Democrats have lost some members since that vote, and more might abandon the bill if they are not satisfied with anti-abortion provisions. Democratic leaders will press for the support of the 39 opponents, but many are from conservative districts where a vote for the health plan could damage their re-election prospects.