Research on human embryonic stem cells has become a bone of fierce political contention in the United States. President George Bush's decision to allow federal funding only for research on stem-cell lines derived before 9 August 2001 has been attacked by his rival, Senator John Kerry, most recently during last week's second presidential debate.

In California, the policy has drawn an even more direct response from the biotechnology industry and parts of the research community. ‘Proposition 71’, on which California's citizens will vote on 2 November, would enable a bond issue that pumps $300 million a year for ten years into research on human embryonic stem cells. The proposition would establish an institute to review grant applications and distribute the funds, and would insulate it from the state legislature, so the money could not be redirected by political whim. The initiative would even amend the state constitution to guarantee the right to do embryo research.

Many researchers in California see this as a chance to flex some political muscle. At first glance, the proposition would close an unfortunate gap in federal research funding and instantly transform the state into a hub of activity in a promising field. But aspects of the proposal should give voters pause before they lend it their support.

First, it isn't clear that this particular field of study can make the best use of the substantial amount of money that the proposition plans to throw at it. In a manner pioneered by campaigners for public funding for sports stadia, the proposition's advocates have delivered a series of “economic analyses” arguing that the bond issue will pay for itself in the long run, by nurturing economic growth through the development of the local biotechnology industry. But it is not clear that these analyses hold water. And the vote is taking place after a series of other ballot-driven commitments to low taxes and high spending, which have driven California to near-insolvency.

The exclusion of the state legislature from responsibility for overseeing the programme is a further cause for concern. Whatever one thinks of individual politicians, democratic supervision places important constraints on the use of public money. The federal agencies that fund most academic research in the United States — the National Institutes of Health (NIH) and the National Science Foundation — operate under the scrutiny of Congress. At these agencies, scientific merit is judged almost entirely by the community itself, but Congress ultimately ensures that the public good is paramount.

Proposition 71, in contrast, would introduce a new model for the support of scientific research at the state level that would rely on mere transparency as a guarantee against abuse. Although public meetings are promised, the oversight committee would consist mainly of people with close ties to the universities, institutes and companies that stand to benefit from the money spent. Most of the rest are representatives of disease groups. The committee makes the ultimate funding decisions and will be allowed to modify NIH rules of informed consent and human-subject protection as it sees fit.

The advocacy of such people as the actor Christopher Reeve —whose untimely death this week deprives biomedical research of one of its most forceful and effective lobbyists — has helped to elevate the promise of embryonic-stem-cell research, sometimes to unrealistic levels. It is up to the people of California whether they want to approve Proposition 71. But if they do, researchers must strive to ensure that no funds will be abused, and they must give full consideration to a wide array of ethical concerns. Anything less risks damaging public trust in science.