Washington ? The Senate soon will debate human cloning, a futuristic science with both enormous promise and frightening implications. Opponents conjure up images of babies cloned for spare parts and laboratory-made Frankensteins, while supporters envision a brave new world where patients with spinal-cord injuries walk again and illnesses such as cancer and diabetes are cured. The two sides will provide the public with a passionate exchange of views. Whether voters will come away enlightened is another matter.

It is easy to demagogue cloning and scare people about a brave new world where ethical boundaries slip away and commercialism takes over. Religious conservatives with the strong backing of President Bush want the Senate to legislate a ban that would bar federal funding for such research. Some women’s groups have come out in support of the ban because they fear women will get seduced into selling their eggs. Those who favor “therapeutic research” propose an alternative that would ban reproductive cloning, but allow experimentation on early cell clusters under tight government regulation. Neither group appears to have the 60 votes needed to cut off a filibuster and pass controversial legislation.

The two sides do not break exclusively along party or even ideological lines. Those who back a full ban are led by Sam Brownback, R-Kan., a leading pro-life voice in the Congress, and Sen. Mary Landrieu, D-La., a pro-choice Catholic. The alternative is co-sponsored by Sens. Ted Kennedy, D-Mass., and Dianne Feinstein, D-Calif., together with Arlen Specter, R-Pa., who has a record of independence from his party’s social conservatives. A wild card is Sen. Orrin Hatch, R-Utah, whose outspoken support for stem-cell research last year angered some religious conservatives but proved crucial in giving Bush the maneuvering room he needed to stray from his political base and allow federal funding.

Explaining the science at the core of the debate requires more than a sound bite. Therapeutic cloning uses an unfertilized egg never implanted into a woman’s uterus, only into a petri dish. This pre-embryonic collection of cells is no bigger than a period at the end of a sentence, and is not fertilized. No sperm are involved. These early embryos are known as blastocysts, and can develop into stem cells valuable for research. When Bush argues that cloning is wrong because “no human life should be exploited or extinguished for the benefit of another,” he is conferring the sanctity of human life on these unfertilized cells.

Bush’s drive to legislate a ban on cloning got a boost when the Senate’s only medical doctor, Sen. Bill Frist, R-Tenn., spoke in support of the ban. Frist does not approach the issue with the same moral fervor as Bush, but claims instead that cloning is not needed right now for stem-cell research to proceed, and that the issue can always be revisited. Some admirers of Frist and he has many think he positioned himself with the president to advance his presidential ambition, either as a potential running mate for Bush or as a candidate on his own in 2008.

Frist admits to having qualms about the ban on importation of cloning research that opponents include in their bill. It creates the specter of desperately ill Americans who seek treatment overseas being subject to arrest when they return.

Even more to the point, what makes anybody think they can legislate science? The rest of the world is not bound to our laws. Worldwide scientific discovery and development only can be thwarted by economic or military coercion, which is what we attempt to employ in our efforts to prevent nuclear and chemical-biological weapons proliferation. This is the real question before the Senate: Is America prepared to use coercion to ensure worldwide compliance with a ban on cloning? The answer may be “yes” to the actual cloning of human beings, but more likely “no” when it comes to stem-cell research.