Candidates' stances on the research are weighing heavily in two key races as the political parties battle for control of the House and Senate in Washington.
But the barrage of campaign ads tends to hide more about stem cell research than it reveals. Ethicists and advocates alike warn that complex scientific issues are nearly invisible in the glare of partisan politics and political sound bites.
What Are Stem Cells?
Stem cells are found in early human embryos within a few days of fertilization. Scientists are interested in them because of their ability to grow into any tissue in the body. That could make them good candidates in the future for curing a range of diseases, such as Parkinson's and diabetes.
Adult stem cells avoid possible ethical pitfalls of embryonic cells, which require an embryo's destruction for harvesting. But scientists backing embryonic research say that embryonic cells are far more versatile than adult cells.
Stem cell research will probably not be the most important issue in most voters' minds on Tuesday, says James G. Gimpel, PhD, a professor of government at the University of Maryland.
"For those people for whom this is the decisive issue, they would have made up their opinion long ago," he says.
But that hasn't stopped stem cells from becoming a major campaign issue in the final weeks of Maryland's Senate race. Actor Michael J. Fox, who suffers from Parkinson's disease, recently starred in a commercial telling voters that Lt. Gov. Michael Steele, the Republican nominee for the seat, opposes stem cell research.
Only a few days later, Steele's campaign released a commercial of its own. Now TV and radio waves are carrying a testimonial from Steele's sister, Dr. Monica Turner, a multiple sclerosis patient, attacking Fox and Rep. Ben Cardin, Steele's Democratic opponent.
"There's something you should know about Michael Steele. He does support stem cell research," Turner states in the commercial.
What the ad doesn't say is at the heart of one of the most confusing parts of the stem cell debate.
Steele has said he supports research on stem cells derived from adult sources like bone marrow. But he backed Bush's July veto because he opposes embryonic research that requires the destruction of embryos to gain stem cells.
"No question that politicians on both sides of the issue articulate it incorrectly," says Sean Tipton, executive director of the Coalition for the Advancement of Medical Research, a pro-stem cell group.
Ads Create Confusion
The Rev. John J. Paris, a professor of bioethics at Boston College and a Jesuit priest, says that while the majority of the public favors embryonic research, ads like Fox's and Steele's have done little to inform voters about the real issues surrounding stem cells.
"What's happening is people's views are being shaped by advertising. I don't think the public has a real clue what stem cells are. Physicians don't know," he tells WebMD.
Nowhere is that more apparent than in Missouri, Paris says. A ballot initiative there asks voters to decide whether the state's constitution should allow embryonic stem cell research and guarantee Missourians access to any cures that arise from the research.
The initiative has sparked a bitter debate between pro-research and pro-life forces. Another commercial starring Fox ran there, as have dozens of other ads for and against the initiative and two Senate candidates in a neck-and-neck race.
Opponents say the initiative promotes human cloning and would coerce women into selling their eggs for research. Supporters argue that cloning is specifically ruled out and that the initiative will promote research into promising new cures.
The Fine Print
Fr the truth, voters would have to turn off the campaign ads and instead delve into the fine print. Stem cell research and cloning are two very different things.
The initiative's legal language bans cloning intended to reproduce a human but exempts a technique known as "therapeutic cloning."
Called somatic cell nuclear transfer, the technique involves extracting DNA from an adult cell and injecting it into a human egg. When the egg divides it produces stem cells genetically identical to the adult cell donor. That can provide an end run around the problem of immune rejection.
Tipton says anti-stem-cell forces are "desperate to confuse people" on the difference between stem cell research and various forms of cloning.
But Patty Skain, executive director of Missouri Right to Life, defends all of her side's ads as accurate and accuses the other side of overhyping the promise of stem cell research.
"They're claiming these cures are going to happen and in fact they have not had one success," she says.
Meanwhile, Paris, sounding frustrated, says both sides are wrong -- and also right. Stem cell opponents make an effort to scare the public with the prospect of mad science run amok, he says. Advocates are guilty of overselling the research and rarely mention that cures, if they come at all, are likely no less than a decade away.
"The issues are driven by emotions and ad dollars and those who have enough money to make their case," he says.
SOURCES: James Gimpel, PhD, professor of government, University of Maryland. Monica Turner, in campaign advertisement for Lt. Gov. Michael Steele. The Rev. John J. Paris, professor of bioethics, Boston College. Sean Tipton, executive director, Coalition for the Advancement of Medical Research. Patty Skain, executive director, Missouri Right to Life.
By Todd Zwillich
Reviewed by Louise Chang