Publicly, President Barack Obama is still calling for a bipartisan bill to overhaul the nation’s health care system. Privately, Democrats are preparing a one-party push, which they feel is all but inevitable.

Obama urged religious leaders Wednesday to back his proposals, and he prepared for a pep talk to a much larger audience of liberal activists, whose enthusiasm is in question. Polls continued to show slippage in support for the president’s approach, although Americans expressed even less confidence in Republicans’ handling of health care.

The administration said it still hopes for a bipartisan breakthrough on its goals of expanding health coverage, controlling costs and increasing competition among insurers. In private, however, top Democrats said a bipartisan accord seems less likely than ever when Congress reconvenes next month.

Obama was to promote his plans Thursday in a conference call and online address to supporters that could draw huge numbers of listeners. He also was to speak with Philadelphia-based radio talk show host Michael Smerconish, who will broadcast from the White House. Smerconish is generally seen as a conservative, although he endorsed Obama last year and supports abortion rights.

Vice President Joe Biden was meeting with health care professionals in Chicago on Thursday to push the administration’s plans. Health and Human Services Secretary Kathleen Sebelius was to join him.

Some Democrats said Democratic researchers have concluded lately that a strong-arm tactic on Senate health care legislation that would negate the need for any GOP votes might be more effective than previously thought.

The strategy, called “reconciliation,” allows senators to get around a bill-killing filibuster without mustering the 60 votes usually needed. Democrats control 60 of the Senate’s 100 seats, but two of their members — Robert Byrd of West Virginia and Edward Kennedy of Massachusetts — are seriously ill and often absent. And some moderate Senate Democrats have expressed reservations about the Democratic-backed health care overhaul plan.

While always contentious, reconciliation lets the Senate pass some measures with a simple majority vote. Non-budget-related items can be challenged, however, and some lawmakers say reconciliation would knock so many provisions from Obama’s health care plan that the result would be “Swiss cheese.”

Democratic aides say they increasingly believe those warnings are overblown.

On Wednesday, Jim Manley, spokesman for Senate Majority Leader Harry Reid, D-Nev., warned Republicans that reconciliation is a real option. The White House and Senate Democratic leaders still prefer a bipartisan bill, he said, but “patience is not unlimited and we are determined to get something done this year by any legislative means necessary.”

In a conference call with liberal religious leaders Wednesday, Obama called health coverage for Americans a “core ethical and moral obligation.” He disputed claims that Democratic bills would create government “death panels” for the elderly, offer health care for illegal immigrants or fund abortions.

“I know that there’s been a lot of misinformation in this debate and there are a some folks out there who are, frankly, bearing false witness,” Obama said. “I need you to spread the facts and speak the truth.”

Administration officials and congressional Democrats were deeply discouraged this week when key Republican lawmakers seemed more critical than ever about various Democratic-drafted health care bills pending in the House and Senate. They said they still hope Senate Finance Committee efforts to craft a bipartisan compromise can succeed, although private remarks were more pessimistic.

“The president believes strongly in working with Republicans and Democrats, independents, any that seek to reform health care,” White House press secretary Robert Gibbs said. “The president strongly believes that we’re making progress.”

Many Republicans believe that millions of Americans, and especially the GOP’s conservative base, ardently oppose Obama’s health care plans, which they consider too costly and intrusive.

Obama’s approval ratings “continue to inch downward,” a Pew Research Center poll concluded Wednesday. Favorable ratings for the Democratic Party also have fallen sharply, although they still exceed those of the Republican Party.

Nearly all sides agree that conservatives showed more energy than liberals this month at often-raucous town halls and other forums on health care. Valerie Jarrett, a top Obama adviser, warned liberal bloggers recently that the health care push is “an uphill battle, and it won’t happen unless we energize our base.”

Many conservatives think they see the first big chink in Obama’s political armor, and Web sites and radio talk shows have encouraged the attacks against his proposals.

Democratic officials, meanwhile, say the often complex and slow-moving health care debate has not captivated millions of liberal activists who campaigned tirelessly for Obama last year.

Organizing for America, the president’s political organization based at the Democratic National Committee, is trying to rally its members. Last week about 60,000 volunteers sent messages to lawmakers, urging them to support Obama’s health care agenda.

Republicans are keeping up their criticisms, and a prominent GOP Senate negotiator warned Democrats not to shut them out.

“If the Democrats choose to go it alone, their health care plan will fail because the American people will have no confidence in it,” Sen. Mike Enzi of Wyoming said Wednesday.

Enzi is one of three GOP senators who have met regularly with Finance Committee members to seek a bipartisan bill.