This week, the Senate will take up legislation already passed by the House (H.R. 810) to authorize federal funding for research on embryonic stem cells harvested by de stroying human embryos left over in fertility clinics. Since August 2001, under a policy established by President Bush, federally funded research has been limited to embryonic stem cell lines that already existed. If the bill passes, the president will veto it. And without the votes to override, the current policy will remain unchanged.

For five years, there has been a sustained effort to overturn the limits set by the president. Advocates of federal funding for research on new stem cell lines have made such funding a litmus test for being "pro-science." Prestigious journals like the New England Journal of Medicine give reports on embryo research special consideration for publication. Meanwhile, advocates downplay advances that do not involve embryo destruction. Reversing the Bush policy--even forcing a veto--would be the crowning achievement of this campaign. It would create, so the thinking goes, a great election issue: Progressives are pro-cure and pro-science. Bush is not.

But as often happens in politics, when momentum builds for a cause, that cause may already be on the way to irrelevancy. The facts on the ground change. H.R. 810 would fund research on so-called "spare" human embryos. Such embryos, however, offer an inefficient and ineffectual road to medical progress: inefficient, because procuring consent to use leftover embryos is a cumbersome process, and the vast majority of couples who produced them do not

While the political fight over the "spares" has raged, some scientists seem to have found a better way forward: a way to get the genetically controlled stem cells they need without destroying human embryos. A second Senate bill (S. 2754), cosponsored by Arlen Specter and Rick Santorum (usually opponents in the embryo research debate), would fund and promote such research. These alternative methods are better ethically, because they do not treat developing human life as raw material; better scientifically, because they would provide designer stem cells; and better democratically, because they do not force those who believe embryo destruction is a grave moral wrong to fund it with taxpayer dollars.

The most important arguments for maintaining the Bush policy are moral: The federal government should not be a party to the destruction of nascent human lives. Yes, such embryos might be left over in fertility clinics, but the fact that they are unwanted does not change what they are or give us a license to destroy them. But even for those who are agnostic about the moral standing of human embryos, a policy that encourages the expanded use of federal dollars for research on "spare" embryos makes little sense when more promising alternatives apparently exist.

Of course, we cannot predict the scientific future--a fact too often ignored by those promising to cure "100 million" Americans if only we funded embryo research without limits. Even the most promising scientific alternatives are speculative. But this much we do know: Destroying more "spare" embryos is unlikely to advance stem cell science significantly. Rather, using federal dollars to fund such research will only lead to demands that further ethical lines be crossed. When using the "spares" doesn't produce results, the demand will be to fund the creation and destruction of embryonic human clones, an even more damaging leap into the brave new world.