WASHINGTON - Defying President Bush's threat to impose his first veto, a broad swath of House Republicans voted with an overwhelming number of Democrats Tuesday to repeal his restrictions on federal funding for embryonic stem cell research.

The action plunges the government deeper into the controversial science that supporters say could lead to cures for debilitating diseases.

The 238-194 vote, unusual because 50 Republicans broke with Bush and top House leaders, followed a highly personalized, occasionally tearful debate in which a parade of lawmakers recounted medical tragedies that had afflicted their families, while opponents contended that the science is built on destroying human lives.

The legislation, which has strong support in the Senate, would make federal money available for research on embryonic stem cells extracted from frozen embryos donated by couples who no longer need them for fertility treatments.

It would lift a restriction imposed by Bush nearly four years ago that limits federally funded research to fewer than two dozen embryonic stem cell colonies, or lines.

The president and other opponents focused on the fact the embryos are destroyed in obtaining the cells. House Majority Leader Tom DeLay, R-Texas, called it a "vote to fund with taxpayer dollars the dismemberment of living, distinct human beings for the purposes of medical experimentation."

"The best that can be said about embryonic stem cell research is that it is scientific exploration into the potential benefits of killing human beings," said DeLay, who set up pro-adoption posters as a backdrop.

DeLay, who had lowered his profile amid the storm over his travel and dealings with lobbyists, spent the afternoon on the House floor leading opposition to the bill.

Breaking party ranks

The vote carried an echo of Monday's Senate deal that averted a showdown over Bush's judicial appointments, with moderate lawmakers working across the aisle to triumph over their leaders.

The stem cell bill, which was opposed by 14 Democrats, was sponsored by Rep. Michael Castle, R-Del., president of the moderate Republican Main Street Partnership, and Rep. Diana DeGette, D-Colo., who spent two years building a winning coalition.

House leaders scheduled Tuesday's vote so that the contentious issue would not be raised repeatedly as an amendment to other critical bills.

Bush said last week that he would veto the bill. With the debate under way at the other end of Pennsylvania Avenue, he underscored his opposition by holding an East Room ceremony surrounded by children whose families had adopted them as embryos.

The same families had appeared several hours earlier on Capitol Hill, with parents and children alike sporting stickers that said, "Former Embryo."

"This bill would take us across a critical ethical line by creating new incentives for the ongoing destruction of emerging human life," Bush said. "Crossing this line would be a great mistake."

Polls have shown that the public is strongly supportive of the research, and Nancy Reagan's backing made the issue politically palatable for many conservatives.

When Bush announced his decision in August 2001 to permit federal funding for the first time for research using a small number of embryonic stem cell lines, the White House estimated scientists would have a choice of more than 60 cell lines on which to conduct federally supported research.

But just 22 lines have materialized, and all of them have been grown in laboratory dishes on layers of mouse cells, making them less than ideal for use in human experiments.

Lawmakers' stories

House Energy and Commerce Committee Chairman Joe Barton, R-Texas, who was among the one-third of Republican committee chairmen who supported the bill, said the loss of his father to diabetes at age 71 and a brother to liver disease at 44 had shaped his decision to support expanded research.

And Rep. Lane Evans, D-Ill., described his own struggle with Parkinson's, saying the disease that is destroying his nerve cells "doesn't keep me from doing the things that are important to me" but does affect every day of his life.

"Only embryonic stem cells hold enormous potential to turn into any cell in the body" and potentially offer him a cure, he said.

But Rep. Dan Lungren, R-Gold River, said his older brother John's 15-year battle with Parkinson's did not obviate his ethical concerns and that he could not support "the destruction of part of the human family."

"The worst mistakes we've ever made in the history of this nation have been when we have defined a part of the human family as less than fully human and done things to them that we would not allow done to ourselves," Lungren said.

"We've done it with slavery; we've done it with the Tuskegee medical experiments" on poor black men with syphilis.

In the Senate, a matching bill has the crucial support of Sen. Orrin Hatch, R-Utah, and Judiciary Committee Chairman Arlen Specter, R-Pa., who have said they plan to capitalize on the momentum from the House.

Sen. Sam Brownback, R-Kan., one of the chamber's leading conservatives, has said he intends to filibuster to try to prevent a vote. Hatch has said he may have enough votes to overcome that.

Republican leaders said they do not think that the bill's supporters can achieve the 290 votes needed to override a Bush veto in the House.

House Rules Committee Chairman David Dreier, R-Glendora, who voted for the bill, said he hopes to negotiate a compromise with the White House to avoid a veto showdown.

Rep. Mike Pence, R-Ind., the leader of House conservatives, called the vote "a successful failure," saying the margin was closer than expected.

Several of the Republicans voting "yes" acknowledged they were breaking voting records they described as "pro-life" and said they were doing so because of their interest in pursuing potential cures for juvenile diabetes, Parkinson's, spinal cord injuries and other ailments.

Across the aisle

Unlike the partisan battles that typically occupy the House, the daylong debate was intensely personal, infused with Biblical references, accounts of family medical tragedies and sharp disagreement over when life begins.

The broad aisle down the middle of the chamber, usually a physical as well as psychic barrier between the parties, was porous for the day as members crossed over to chat with the opposition.

Proponents of the bill argued Bush's 2001 limits on federal funding have hampered potentially promising treatments for a range of illnesses and put the United States at a competitive disadvantage with nations that have pursued the research more aggressively.

Rep. Christopher Shays, R-Conn., called his support "one of the most important votes I will ever make in Congress."

"I think it's time we recognized the Dark Ages are over," Shays said.

"Galileo and Copernicus have been proven right. The world is in fact round; the Earth does revolve around the sun. I believe God gave us intellect to differentiate between imprisoning dogma and sound ethical science, which is what we must do here today."

Opposing the bill, House International Relations Committee Chairman Henry Hyde, R-Ill., drew scattered applause when he compared the legislation to the failure of a former generation to recognize the humanity of Dred Scott, the slave whose suit for his freedom led to a landmark Supreme Court ruling.

"For the first time in our national history, taxpayers' dollars are going to be spent for the killing of innocent human life," Hyde said.

"We're going to pay a terrible price for not recognizing the humanity of these little embryos."

The small, vigorous group of opponents lobbied instead for more research on stem cells that are harvested from bone marrow and other organs, such as the pancreas or liver, and perhaps the umbilical cords of newborns.

House leaders paired the Castle-DeGette bill with legislation promoting research on stem cells derived from discarded umbilical cord blood.

Cord blood cells have cured dozens of diseases, but those achievements have been limited to diseases of the blood. That bill passed 430-1.