WASHINGTON - Victory within reach, President Barack Obama exhorted House Democrats on Saturday to stay true to their party's legacy and make history by bringing health insurance to millions of struggling families now left out. Leaders exuded confidence as they defused thorny problems in the countdown to a landmark vote.

Obama evoked Abraham Lincoln's moral compass and extolled Democratic achievements such as Social Security and Medicare - once controversial, now an essential part of the social fabric - on a day marked by a frenetic hunt for votes inside the Capitol and angry tea party demonstrations at the door. Some protesters hurled racial insults at black members of Congress.

"Is this the single most important step that we have taken on health care since Medicare?" Obama asked rank-and-file Democrats far from the chanting crowds. "Absolutely. Is this the most important piece of domestic legislation, in terms of giving a break to hard working, middle-class families out there since Medicare? Absolutely.

"It is in your hands," Obama said, bringing lawmakers to their feet. "It is time to pass health care reform for America and I am confident that you are going to do it tomorrow."

In a carefully orchestrated appeal to unity ahead of a career-defining vote, Obama and House leaders were joined by Senate Majority Leader Harry Reid, D-Nev., who brought a pledge from more than 50 of his Democratic colleagues to promptly finish the bill after the House votes today. House Democrats have been wary of being left in the lurch by the famously unpredictable Senate.

A series of last-minute flare-ups threatened to slow the Democrats' march to passage, after more than a year of grueling effort.

The most intense focus was on a small group of Democrats concerned that abortion funding restrictions in the legislation don't go far enough. Determined to avoid votes on such a charged issue, Democratic leaders raised the possibility of addressing the concerns of abortion foes through an executive order from Obama. It would reaffirm existing federal law barring taxpayer funded abortions except in cases of rape, incest or to save the life of the mother.

House Democratic leaders abandoned a much-challenged procedure for passing the legislation after an outcry from Republicans and protest from some of their members. According to the new plan, the House will vote up or down the health care bill passed by the Senate on Christmas Eve as well as a package of changes.

The Senate bill would then go to Obama for his signature, the companion measure to the Senate, which hopes to pass it within the week.

Minutes after the leadership's change of heart, Rep. Dennis Cardoza, D-Calif., announced his support for the health care legislation. Cardoza had criticized the planned maneuver.

The 10-year, $940 billion measure represents the biggest expansion of the social safety net since Medicare was enacted more than 50 years ago. It provides health coverage to 32 million people now uninsured, bars insurance companies from denying coverage to those in poor health, and sets up new marketplaces where self-employed people and small businesses can pool together to buy coverage. Less certain is whether it will also deliver on Obama's promise to slow the punishing pace of health care costs.

Republicans, unanimous in their opposition, complained anew about the bill's cost and reach. Senate GOP Leader Mitch McConnell of Kentucky said a fuller analysis of the bill's long-term costs is needed, but Democrats have left no time to carry it out.

Displaying a gritty confidence, House Democratic leaders said they were getting closer by the hour. "We are on the verge of making great history for the American people," said House Speaker Nancy Pelosi, D-Calif.

In a flashback to the day in 2007 when Obama announced his presidential bid in Springfield, Ill., the president repeatedly evoked Lincoln's perseverance in the face of divisions - "We are not bound to win, but we are bound to be true."

Obama praised two first-term Democrats who switched from no to yes - Colorado's Betsy Markey and John Boccieri of Ohio - for staying true to Democratic principles.

"I know this is a tough vote," the president said, adding he also believes "it will end up being the smart thing to do politically."

He told lawmakers: "This is one of those times where you can honestly say to yourself, doggone it, this is exactly why I came here. This is why I got into politics. This is why I got into public service."

Obama's appearance came on a frantic day bordering on the surreal and sometimes turning ugly.

Inside the Capitol, Democratic leaders pursued the last few votes to reach the 216 needed to pass the sweeping legislation, sometimes in full view on the House floor. Several thousand demonstrators opposed to the bill swirled on nearby streets, with some surrounding lawmakers between the Capitol and their offices.

Obama's motorcade was delayed, and as he rode up to Capitol Hill, many of the protesters booed and gave him a thumbs down.

Scores crowded into one House office building entranceway booed loudly when liberal Rep. Barney Frank, D-Mass., walked by.

Rep. Andre Carson, D-Ind., said that as he left the Cannon House Office Building with Rep. John Lewis, D-Ga., a leader of the 1960s civil rights movement, some among the crowd chanted "the N-word, the N-word, 15 times." Both Carson and Lewis are black. Lewis spokeswoman Brenda Jones also said the incident occurred.

"It was like going into the time machine with John Lewis," Carson said.

Kristie Greco, spokeswoman for Democratic Whip Jim Clyburn, D-S.C., said a protester spit on Rep. Emanuel Cleaver, D-Mo., who is black.

Clyburn, who led fellow black students in integrating South Carolina's public facilities a half century ago, called the behavior "absolutely shocking."

"I heard people saying things today that I have not heard since March 15, 1960, when I was marching to try to get off the back of the bus," Clyburn told reporters.

Democratic leaders and Obama focused last-minute lobbying efforts on two groups of Democrats: 37 who voted against an earlier bill in the House and 40 who voted for it only after first making sure it would include strict abortion limits that now have been modified.

The pressure remained intense even for those who had decided. Rep. Stephen Lynch, D-Mass., who switched from yes to no, received a scathing letter from labor unions in his state.

Lawmakers said House leaders settled one major issue complicating passage of the bill, concern from lawmakers in states with low health care costs that Medicare payments for hospitals and doctors are too paltry.

It was unclear how the leaders would resolve the dispute over abortion, or if they could avoid it.

Rep. Bart Stupak, D-Mich., who succeeded last November in inserting strict anti-abortion language into the House bill, had hoped to do so again. Pelosi met Saturday with three undecided lawmakers who are part of Stupak's group and hoped to peel them off. She succeeded with at least one, Rep. Chris Carney, D-Pa.

Associated Press writers Erica Werner, David Espo and Chuck Babington contributed to this report.