Several key lawmakers have flipped their vote from a "no" to "yes" in recent days, including Rep. Dennis Kucinich, D-Ohio, Rep. Dale Kildee, D-Mich., Bart Gordon, D-Tenn., and Rep. Betsy Markey, D-Colo.
The roughly dozen Democratic members of Congress who have still not declared whether they wouldl support it want more stringent language on federal funding for abortion. Other liberal members said the bill doesn't go far enough to protect Americans.
After the House passes the health care bill, it has to be voted on in the Senate, so it could be days before it actually lands on President Obama's desk. Pelosi today said that when members of the House vote for the health care bill, they will have assurances from the Senate that it would also pass the same legislation.
The Senate GOP leadership argues the House vote does not signal the end of the health care debate.
"I think any House Democrat that votes for this bill thinking the Senate is going to clean up the mess is delusional," Senate Minority Leader Mitch McConnell, R-Ky., told ABC News' Jonathan Karl today. "I don't think it will pass in the same form."
Others are promising a tough fight in the Senate.
"Well, let me put it to you this way, it's far from going to pass in the Senate," Sen. Orrin Hatch, R-Utah, said in an interview with Bloomberg Television's Al Hunt to air tonight. "I think there'll be at least two major points of order raised, and we'll win on those points of order, which means it has to go back to the House. If those people think they're only going to vote on this once, they're nuts."
With the momentum for the health care debate gaining pace, the president on Thursday again postponed his trip to Australia and Indonesia to June.
The House vote is expected to take place on Sunday, although lawmakers said it could also be pushed back to Monday.
A new poll released today showed Americans are closely divided on the health care overhaul bill. A poll by the Kaiser Family Foundation, conducted in March, found that 46 percent supported the legislation while 42 percent opposed it. Forty-two percent said it's time to take a vote, while 36 percent said they want lawmakers to "to go back to the drawing board and start over again." The rest, two in 10, wanted Congress to drop it entirely.
Of those polled, 45 percent thought they would be better off with reform than without it, and 33 percent said they wouldn't be.
Republicans continue to staunchly oppose the Democrats' health care bill and warned about its consequences.
"If anyone thinks the American people are going to forget this vote, just watch," House Minority Leader John Boehner, R-Ohio, warned today.
Democratic Rep. Bart Stupak if Michigan said today he's open to a deal but will vote "No" on the health care bill unless changes are made to accommodate his more-stringent language that prevents federal funding for abortions.
Stupak's amendment, which was part of the House bill but failed in the Senate, limits access to abortions for people who receive federal subsidies and those who purchase insurance through a health insurance exchange, a marketplace in which people could shop for and compare insurance plans.