President Barack Obama greets the audience after speaking about health care reform at the Patriot Center at George Mason University in Fairfax, Virginia, Friday. (AP)

WASHINGTON (AP) – The long, turbulent struggle over landmark health care legislation tilted unmistakably in President Barack Obama’s favor as one by one, undecided Democratic lawmakers began choosing sides Friday.

In full campaign mode, his voice rising, the president all but claimed victory, declaring to a cheering audience in Virginia, “We are going to fix health care in America.’’

With the showdown vote set for Sunday in the House of Representatives, Obama decided to make one final, personal appeal to rank-and-file Democrats, arranging a Saturday visit to the Capitol. Obama has put his presidency on the line to gain passage of his top domestic priority in the face of unanimous opposition from Republicans who say the plan amounts to a government takeover of health care that will lead to higher deficits and taxes.

The health care reform program would affect nearly every American and remake one-sixth of the US economy. For the first time Americans would be required to have health care insurance and face penalties if they refused. The United States is the only major industrialized country that does not have a comprehensive national health care plan.

Obama, who delayed a trip to Indonesia and Australia to help ensure passage of the legislation, spoke to an enthusiastic crowd at a suburban university, lobbing attacks at the insurance industry with his jacket off and sleeves rolled up. “The only question left is this: Are we going to let the special interests win once again, or are we going to make this vote a victory for the American people?’’ he said.

Under a complex and controversial procedure Democrats have devised, a single vote will likely be held in the House to endorse a bill approved by the Senate last year as well as a second measure with a package of fixes agreed to in negotiations with the White House. The Senate would then use a procedure called reconciliation to pass the fix-it measure that requires only a simple majority of 51 in the 100-member body, avoiding Republican delaying tactics.

One day after House Democrats released 153 pages of revisions to their bill, Democratic leaders were scrambling to gather the 216 votes they needed for passage, so every undecided lawmaker was the focus of personal attention from the leader of the House, Speaker Nancy Pelosi, and the White House. They focused lobbying efforts on two separate groups of Democrats, 37 who voted against an earlier health care 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.