President Bush and his Democratic Party challenger, John Kerry, have staked out sharply different positions on the controversial subject of embryonic stem cell research. Scientists say the use of cells from human embryos could lead to treatments for a wide variety of diseases and medical conditions. But American scientists are warning that federally funded research of existing stem cell lines is of limited value. VOA's Michael Bowman examines the heated political debate about stem cell research, and how the controversy is putting the scientific community under a microscope.

For years, Americans have been told of the miraculous potential of human embryonic stem cells, which are formed in the earliest stages of life and can adapt to become any tissue in the body. Democratic Party presidential hopeful John Kerry has repeatedly called for expanding stem cell research.

"I believe, if we have the option, which scientists tell us we do, of curing Parkinson's [disease], curing diabetes, a spinal cord injury, anything! That is the nature of the human spirit," Mr. Kerry said. "I think it is respecting life to reach for that cure."

But embryos have to be destroyed when stem cells are harvested, a fact that ignites passions and fuels controversy. President Bush takes the position that all human life, in all stages of development, is sacred. It therefore came as a surprise to many of his Republican allies when, in 2001, he endorsed federal funding for stem cell research. But the president restricted research to a small number of existing stem cell lines where the embryo had already been destroyed - or, as Mr. Bush has noted, "where the life-and-death decision had already been made."

"Embryonic stem cell research requires the destruction of life to create a stem cell," Mr. Bush said. "I am the first president ever to allow federal funding for embryonic stem cell research. I did so because I, too, hope we will discover cures from the stem cells. But I think we have to be very careful in balancing the ethics and the science."

As a group, the scientific community strives to be non-political, and the emergence of embryonic stem cell research as a contentious issue in this year's presidential race has put researchers in an uncomfortable position. Addressing a recent gathering of top stem cell researchers in Washington, Harvard Medical School professor George Daley tried his best to appear non-partisan as he made a plea for access to more embryonic stem cell lines.

"I think President Bush is to be given credit for recognizing the enormous scientific value of these cells," Mr. Daley said. "But I have been frustrated as well, because the way the policy was crafted limited us to the stem cell lines that existed at the time. Since the policy was announced, we now have an enormous number of additional embryonic stem cell lines, some of which model human disease and would be important reagents for our studies, but unfortunately for which we cannot use our federal money. Embryonic stem cells are invaluable research tools. We hold hope that it will be a new modality of medicine, and for that we would need an expansion of the current presidential policy."

Mr. Daley notes that embryonic stem cell research is progressing in several dozen countries, many of which do not operate under restrictions like those imposed by the Bush administration in the United States.

Scientists say they hope public opinion surrounding stem cell use will be molded by facts, not political rhetoric. James Battey is a researcher with the National Institutes of Health, which funnels much of the federal funds used in medical research in the United States.

"There is a tremendous thirst for knowledge out there," Mr. Battey said. "There is also a lot of public opinion being formed based on very bad information. And I think there is room for people to have many different points of view about this research. I would just make a plea that those points of view be formulated based on factual information and not misinformation."

Even the most optimistic researchers caution that actual cures for diseases like Parkinson's may be many years away, with or without expanded access to embryonic stem cells in the United States. While many scientists involved in the research appreciate John Kerry's position in favor of stem cell research, some say they worry that the candidate's pronouncements may raise false hopes among the general public, including the very ill, that wondrous cures are just around the corner.