In a rare ceremonial gesture reserved for major votes, senators cast their yeas and nays from their desks in the chamber, each one rising to voice his or her position. Senator George V. Voinovich, Republican of Ohio, was not present and did not vote.

After the vote, Mr. Reid said he understood that Ms. Landrieu was already working with two other Democratic senators, Thomas R. Carper of Delaware and Charles E. Schumer of New York, to see if they could devise a public insurance plan with broad appeal.

The White House issued a statement praising the vote. “The President is gratified that the Senate has acted to begin consideration of health insurance reform legislation,” his press secretary, Robert Gibbs, said, adding that President Obama “looks forward to a thorough and productive debate.”

Mrs. Lincoln, who faces a tough re-election campaign next year and has in recent weeks been the target of millions of dollars in television advertising by both sides in the health care fight, said pointedly that she would not vote for the measure if it retained a government-run health insurance plan, known as the public option, to compete with private insurers. “Although I don’t agree with everything in this bill, I believe it is more important that we begin debate on how to improve the health care system for all Americans,” said Mrs. Lincoln, who was the last uncommitted Democrat, and whose speech, at about 2:30 p.m. Saturday, lifted a cloud of suspense that had hovered around the Capitol.

She added: “But let me be perfectly clear. I am opposed to a new government-administered health care plan as a part of comprehensive health insurance reform, and I will not vote in favor of the proposal that has been introduced by leader Reid as it is written.” But Senator Lieberman, who voted to take up the health care bill, said he was still staunchly opposed to a government-run plan. It is “a terrible idea,” he said.

Ms. Landrieu, whose support came after she won a provision that could be worth more than $100 million in additional federal aid for her financially troubled state, said, “I have decided there are enough significant reforms and safeguards in this bill to move forward, but much more work needs to be done.”