Last week, the US House of Representatives voted by 238 to 194 to reverse the policy restricting embryonic stem-cell research that was implemented by President George W. Bush back in 2001 (see page 544).

The measure will now be taken up by the Senate, where it has a good chance of success. However, Bush said both before and after the House vote that he will veto the measure if it reaches his desk. Even that won't erase the significance of this first victory in the Republican-controlled House for advocates of stem-cell research. The fact that 50 Republican members voted for the change in policy underlines the fact that the pendulum of public opinion is swinging strongly in favour of allowing more of the research to go ahead.

That augers well for the eventual loosening of federal policies that have kept scientists' hands tied in the United States. Some influential Republicans — including Nancy Reagan, the wife of a former president, and conservative Utah senator Orin Hatch — have spoken out in favour of embryonic stem-cell research, making it easier for others to publicly support the work as well.

Indeed, the desperate language used by opponents of embryonic stem-cell research suggests they know they are losing the debate. Tom DeLay (Republican, Texas), majority leader in the House, said on Tuesday last week that a vote for the stem-cell bill was a vote “to fund with taxpayer dollars the dismemberment of living distinct human beings for the purposes of medical experimentation”.

There's no indication that the public is buying this. Polling evidence suggests that most Americans instead have high hopes for the research, and biomedical advocacy groups have done an effective job convincing lawmakers that the research deserves a chance to fulfil these hopes. Years of tireless lobbying by these groups played a major role in the 24 May victory. So too did competitive pressure from overseas, with South Korean research making headline news just ahead of the vote, and from state governments, whose own initiatives in this sphere are forging ahead in California, New Jersey and elsewhere.

Even if the measure passed by the House becomes law, the United States would retain more restrictions on publicly funded research than do nations such as South Korea and Britain, both of which allow publicly supported scientists to use somatic cell nuclear transfer to derive fresh embryonic stem-cell lines. The US measure would allow federal funding only for work on embryos left over from in vitro fertilization clinics.

In the Senate, Sam Brownback (Republican, Kansas) has already said that he will attempt to block a vote on the stem-cell measure, so that for the measure to pass it will need the support of 60 out of the 100 senators. If it obtains these votes, the bill will arrive on President Bush's desk — and he'll face a difficult choice.

The proponents of stem-cell research have mooted the idea of some sort of compromise, which might, for example, update the 2001 policy to allow publicly funded work on more recently derived stem cells. But the president has chosen to draw what he sees as a moral line in the sand that he feels he cannot cross. He has threatened to make this the first bill that he has vetoed in four-and-a-half years in office. But the veto, if it is used, will place him squarely against public opinion in the United States, which increasingly views embryonic stem-cell research not with fear, but with hope.