The new Democratic leadership in Congress thinks it has a winning issue and possibly the votes to defy President Bush on stem cell funding. But an announcement this week by scientists at Harvard and Wake Forest universities appears to vindicate his policy and may relegate the national debate over stem cell research to a political side show.

Researchers have found that amniotic fluid is a fertile source for the kind of stem cells, called pluripotent, that can turn into several types of human cell tissue and potentially cure diseases. They already have succeeded in converting these stem cells into brain, liver, and bone cells, and even into heart cells that could grow to be replacement heart valves.

For five years, Democrats have sharply criticized the president’s policy, with Democratic candidates making the issue a mainstay of their advertisements. The president has been all but blamed for the fact that millions of Americans with diseases and disabilities have not been cured. Most famously, in a speech at the last Democratic National Convention Ronald Reagan Jr. said that stem cell research “may be the greatest medical breakthrough in our or in any lifetime” and that these cells could “cure a wide range of fatal and debilitating illnesses: Parkinson’s disease, multiple sclerosis, diabetes, lymphoma, spinal-cord injuries, and much more.”

In order to understand the criticism of the president’s stem cell policy, it is important to recall what he actually decided on August 9, 2001. At the time, federal funds had never been used to support research on embryonic stem cells. Although the president wanted to open the door to government funding for seemingly promising medical research, he objected to the fact that taxpayer dollars might be used to support or encourage the destruction of human embryos, which were believed to be the only source of embryonic stem cells. So the president struck a compromise. He allowed federal funding, but only on stem cell lines that were already in existence — as he put it, “where the life and death decision had already been made.”

In early 2001, the president met with prominent scientists who told him that even a few stem cell lines would be sufficient to determine whether embryonic stem cell therapies were viable. In an interview a few weeks before the president’s decision, Stanford University researcher Irving Weissman said that “a finite number would be sufficient. If we had 10-15 lines, no one would complain.” Yet almost from the day the president announced his policy, the most often heard criticism has been that it does not permit sufficient stem cell research.

Initially, there may have been some credence to this argument. Throughout the latter half of 2001, only one stem cell line was available to researchers, in large part due to intellectual property issues and the reluctance of foreign institutions to make their lines accessible. But by 2003, 12 lines were available for federal funding, and today there are 22. These 22 lines have resulted in more than 700 shipments of stem cells to federally funded researchers, and the National Institutes of Health is poised to make thousands more available upon request. Moreover, given the absence of any restrictions on privately funded stem cell research, one imagines that if pharmaceutical companies believed that such therapies were indeed viable, there would be no shortage of private capital investment in the field.

At any rate, thanks to the development of new technologies and methods, many of which were developed with federal funds made available by the president’s policy, there appear to be multiple sources of embryonic stem cells whose derivation does not require embryo destruction. The president’s Council on Bioethics in May 2005 laid out several potential ways for harvesting embryonic stem cells without destroying embryos, and all of them have since been attempted and detailed in scientific journals.

The possibility of cell re-programming also is promising. Scientists from Japan’s Institute for Frontier Medical Science have shown that altering just four genetic factors was sufficient to change adult cells into pluripotent stem cells. If this technique proves successful, it will allow an ample supply of these stem cells without the ethical complications of embryo destruction.

And now the news from Harvard and Wake Forest researchers is the most promising of all. If their work stands the test of time, there will be little argument that taxpayers should be forced to underwrite what many believe is the destruction of human life. As Congress prepares to override the president’s stem cell policy, and as the president prepares to use his veto pen for only the second time — the first time was also to block stem cell legislation — we should keep in mind that science sometimes can get in the way of a good political fight.

Mr. Lefkowitz served as a domestic policy adviser to President Bush between 2001 and 2003.