The announcement in November of 2006 that researchers in the United States and Japan had succeeded in turning skin cells into what appeared to be the equivalent of embryonic stem cells transformed the landscape of stem cell science, and the related ethical debate. If Democrats in Washington ever notice it, it might even transform the political debate.

One of the key caveats at the time, however, was that the technique required the use of a virus to introduce several genes into the skin (or other) cell, and these would remain in the cell, and so might contaminate the resulting stem cell or create cancer risks. A few months ago , a team at Harvard succeeded in reprogramming cells using a virus that did not integrate into the cell’s DNA. And today , in the journal Nature , a group of Canadian and British researchers report that they have done it without using a virus at all. Their technique leaves no trace of the gene factors it uses. As Harvard’s George Daley put it, “this type of strategy certainly leaves the cell genetically pristine.” If their results are confirmed by others, they eliminate yet another argument from the arsenal of those who want to use taxpayer dollars to support and encourage the destruction of embryos for research.

There is little left in that arsenal now except the desire to study embryos themselves—to better understand human development. There is knowledge to be gained by such studies, of course, but it hardly makes for the sort of case embryo-research advocates were advancing just a few years ago—with its miracle cures and treatments for the untreatable.

Some people see simply no ethical problem at all with destroying embryos for research, and for them the study of embryos for its own sake is certainly worth public support (we support all kinds of basic research after all, rightfully so, and this basic research could be of more value than most). For others (myself included), the destruction of developing human beings for research is simply unethical as a matter of principle and should not be supported.

But for most Americans, this seems to be a question of balance. Given the ethical questions at stake, is the medical promise sufficient to make us put the ethical concerns aside and support the research? That balance has changed considerably in the past few years, as alternative avenues of stem-cell science have opened up and it increasingly seems like whatever therapeutic potential such cells may someday have could be explored and achieved without the destruction of embryos.

President Obama seems likely to change the government’s policy on the subject soon, and begin for the first time to support embryo-destructive research with taxpayer dollars. But even as he does so, the underlying science may well move the politics of stem-cell research in the other direction.