Emerging from marathon talks with Majority Leader Harry Reid and White House officials late Friday night, Nelson said "real progress" had been made toward his call for greater restrictions on abortion within the legislation.
Majority Leader Harry Reid decided to go public a final package of changes in the long-debated legislation on Saturday "and is confident that it will prevail," his spokesman, Jim Manley, said in a late-night statement.
Reid made no comment to reporters, but Sen. Chuck Schumer, D-N.Y., another participant in the talks, sounded pleased. "I've been in Harry Reid's office for 13 hours and I'm glad to get out of there," he said. "But I'm particularly glad with what has happened in that office."
With Nelson's vote, Obama's Senate allies would have the 60 needed to overcome a filibuster by Republicans.
That gave Nelson enormous leverage as he pressed for concessions that included stronger restrictions on abortions to be covered by insurance policies offered in a newly overhauled health care system. Officials said he was also seeking to ease the impact of a proposed insurance industry tax on nonprofit companies, as well as win more federal funds to cover Nebraska's cost of treating patients in Medicaid, the state-federal health care program for the poor. These officials, speaking on condition of anonymity because of the sensitivity of the talks, said the administration and Democratic leaders had offered concessions on those points.
The Nebraska Democrat has already rejected one proposed offer on abortions as insufficient, and the presence in the talks of Sen. Barbara Boxer, D-Calif., indicated additional changes were on the table.
Boxer has a strong record in favor of abortion rights. She told reporters as she left the Capitol at the end of the evening there had been progress made on the issue of separating personal funds, which may be used to pay for abortions, from federal funds, which may not.
The issue is contentious because the legislation provides federal subsidies to help lower and middle-income families afford insurance and the other federal health care programs ban the use of government money to pay for abortions.
Obama devoted his weekend radio and Internet address to the issue he campaigned on in 2008.
"Now - for the first time - there is a clear majority in the Senate that's willing to stand up to the insurance lobby and embrace lasting health insurance reforms that have eluded us for generations," Obama said. "Let's bring this long and vigorous debate to an end."
"As this difficult year comes to a close, let's show the American people that we are equal to the task of meeting our great challenges," he said.
In the Republican response, Sen. John McCain warned that rushing through legislation now would do more harm than good.