ABC News' George Stephanopoulos reports that Speaker of the House Nancy Pelosi, D-Calif., and the Democratic leadership had been lobbying AARP for weeks. Officials of the organization also met Tuesday with White House Chief of Staff Rahm Emanuel and took the proposed endorsement to their board of directors.
AARP's support could provide fresh momentum to Pelosi's overhaul efforts as the Democratic leadership scrambles to get the 218 votes it needs to pass legislation on the floor.
The American Cancer Society Cancer Action Network, the advocacy arm of the American Cancer Society, also today backed the House Democrats bill, saying it will improve health care for cancer patients and their families.
"This legislation represents an exceptional opportunity to advance our mission of reducing suffering and death related to cancer," Chief Executive John R. Seffrin said in a statement.
House Democrats are determined to pass the $1.055 trillion, 10-year bill by the week's end, but they need the support of centrist Democrats, some of whom are skeptical about language on abortion and illegal immigrants.
No Republicans are expected to support the legislation, which, they still argue, entails a government takeover of Americans' health care system.
Today, the mood on Capitol Hill today was one of anger as "tea-party" protestors, led by Rep. Michele Bachmann's, R-Minn., came in droves and in buses from various states to protest Democrats' agenda. House Republican leadership also held a press event at noon to register their criticism.
"The Democrats do not have the American people and their best interest at heart," Linda Giresi, who came from Union, N.J., told ABC News. "They have their own self interests at heart. And that is the root of this 2,000 page outrage."
Pelosi expressed confidence today that there will be enough votes to pass the bill, adding that she is "excited about being on the brink of passing historic health care legislation."
"We are on our path. We're very excited," she told reporters.
The speaker also hailed the support of the American Cancer Society while criticizing the large profits posted by some health care insurance providers like Cigna.
Majority Leader Steny Hoyer, D-Md., predicted that the House will pass overhaul legislation Saturday, but he admitted that it could be a close vote.
"I wouldn't refer to it as a squeaker, but I think it's going to be close," Hoyer said today in an interview with wire service reporters. "This is a huge undertaking."
Hoyer also said that the bill's endorsement by AARP was a significant boost. He added that the provisions on abortion and illegal immigrants were still being worked out but predicted those issues could be solved in time for Saturday's scheduled debate and vote.
House Democrats say their legislation would insure 36 million more people in the next 10 years, covering 96 percent of all Americans. That is more than the Senate bill currently being negotiated, which would cover an estimated 29 million additional people.
The House bill would also expand Medicaid coverage and provide more support to low-income citizens.
Democratic leaders argue that it would not add a dime to the deficit, an important factor considering President Obama has said he will not sign any legislation which does so.