That's why the basis for a veto is "unfortunate," said Judi Hilman, executive director of the Utah Health Policy Project. The idea that expanding the program marks the beginning of socialized medicine because middle-class children will be eligible — "is based on false premises, and points out just how broken our system of health care has become."

In general, supporters said it would extend coverage to children of families making up to 300 percent of the federal poverty level, or about $62,000 for a family of four.

At that level, congressional officials said, it would cover about 4 million children who now go without, raising the total for the program overall to 10 million kids. The $35 billion cost over five years would be covered by an increase in the tobacco tax of 61 cents a pack.

The vote unfolded one week after the House failed to override Bush's earlier veto, and indicated that the changes Democrats had made failed to attract much, if any, additional support.

The 265 votes cast for the measure was seven shy of the two-thirds majority needed to override a veto. In addition, 14 Republicans who voted to sustain Bush's original veto were absent.

Public opinion polls show widespread support for the issue, and the political subtext was never far from the surface in the debate.

The children's health measure has emerged as one of the most contentious issues of the year, temporarily supplanting last winter and spring's fierce debate over the Iraq war.

"There may be some particular loyalty to the president," Rep. Charles Rangel said in remarks aimed at Republican opponents of the legislation. "But you have to remember than when these voters come to you the president's veto message will not be stapled to you and you will have to be able to explain your vote," added Rangel, the chairman of the House Ways and Means Committee.

"This bill is not going to become law," countered Rep. John Boehner of Ohio, the Republican leader. "If you're tired of the political games, if you're tired of Congress' approval rating being at these ridiculous levels, let's all just vote no."

Democrats, sensing a political advantage, were having none of that.

"God willing, President Bush will sign this bill," Speaker Nancy Pelosi, D-Calif., told reporters at a news conference — less than an hour before the White House issued a statement saying he would not.

The bill "continues to move children from private health insurance to government programs; provides insufficient safeguards to assure that funds will not be spent on ineligible individuals; and, remarkably, actually costs more than the earlier bill, not withstanding supposed improvements in policy," it said.