When Ronald Prescott Reagan takes the stage tomorrow night at the Democratic National Convention to promote human embryonic stem cell research, it will be more than a political poke in the eye to the man running as the heir to President Ronald Reagan's legacy. It will be a public relations coup for proponents of the research and could bolster a fresh line of attack against President Bush on a host of medical and scientific issues, according to advocates and political analysts.

"This indicates to me Democrats clearly decided to make this an issue in the campaign, which is significant," said Rep. Michael N. Castle (R-Del.).

Nearly three years after Bush announced his compromise position permitting federally funded research on a limited number of embryonic stem cell colonies, there is growing frustration among scientists and patients advocates that the restrictions have severely slowed potential medical breakthroughs and left the United States lagging behind other nations in research.

The rising concern has prompted even traditionally apolitical scientists to become increasingly vocal in their criticism of Bush and mount an effort on behalf of his Democratic opponent John F. Kerry, who has promised he would lift the Bush restrictions.

"Certainly more than I've ever seen before, more scientists are engaged in outspoken advocacy for Kerry as the alternative to Bush because of Bush's apparent negatives on support for science," said Mary Wooley, president of the nonpartisan Research America, which advocates increased investment in science.

"Stem cells is the icon for a lot of the frustration, but it goes much deeper than that," said Henry Kelly, president of the Federation of American Scientists, who is forming a pro-Kerry group. "No doubt this is an unnatural act for most scientists. Like it or not, the issues scientists deal with have become the issues of the big leagues of politics."

The critique against Bush is summarized in the phrase "ideology trumps science," Kelly said. He and others cite Bush's emphasis on abstinence-only sex education, appointments to scientific advisory panels based on moral views, the removal of scientific findings from government Web sites, and proposing slowing the growth of the budget for the National Institutes of Health.

"Bush Senior was friendly to science. He took his science counsel very seriously," said Harold Varmus, a Democrat and former director of the NIH who will chair the new group Scientists and Engineers for Kerry. "His science adviser was very high-ranking. He seemed like a genuinely curious person. Scientists feel a very different atmosphere right now."

Bush allies and some detractors credit him for completing the doubling of the NIH budget and for allowing some tax money to go into research on 5-day-old embryos called blastocysts. They discount the appearance by Reagan's son as a partisan publicity grab that will be long forgotten by Election Day.

"I guess it means those who run the convention want to position the Democratic Party's support for embryonic stem cell research as the royal road to curing the sick," said Richard Doerflinger, deputy director of abortion-opposition activities at the U.S. Conference of Catholic Bishops. The effort's success "depends on how gullible the American people are."

Jay Lefkowitz, a former senior adviser to Bush who was instrumental in the stem cell decision, said Bush's stance "puts him squarely in line" with Ronald Reagan's views on life beginning at conception.

But public outpouring over Reagan's death and the outspokenness of his son and wife about the potential of stem cells to treat or cure illnesses such as Parkinson's and diabetes and spinal cord injuries have propelled patients groups and researchers into the campaign fray.

"Up until the day he died, it was a science debate," said Kevin Wilson, director of public policy at the American Society for Cell Biology. "Now it has been thrown into a much larger context."

Recognizing that the war in Iraq and the economy will loom large in the November election, Democrats and pollsters nevertheless say that science -- particularly stem cell research -- is the sort of "crossover" issue with the potential to attract independent voters and undecided moderate Republicans.

"I think all these other events may swamp it, but this is not an issue you can run and hide from," said Republican pollster Robert Moran, who has done extensive polls and focus groups on stem cell research. "If this is going to negatively impact President Bush, it will likely be in places like the Philadelphia suburbs, where you have moderate swing-voting economic conservatives."

An NBC News-Wall Street Journal poll conducted last month found that more than 70 percent of voters supported medical research using embryonic stem cells. Even voters who identified themselves as "strong Bush supporters" backed the research by 58 percent. Told of the results, GOP pollster Whit Ayres said: "That gets your attention."

In recent weeks, conservatives such as Sen. Trent Lott (R-Miss.) and Rep. Dana Rohrabacher (R-Calif.) have changed positions, urging Bush to loosen research restrictions. The issue has divided GOP Senate candidates in Florida and was the topic of a recent radio address by Kerry.

"Anyone who knows Politics 101 can count 128 million people" suffering from illnesses who could benefit from stem cell research, said Doug Wick, a Hollywood producer and research proponent. "That's a huge amount of voters. What could be more basic than the health of their families?"

Former senator Connie Mack (R-Fla.), who supports expanding the Bush policy, said it is unlikely that stem cells will be a top-tier issue in November.

"It may be of help to the Democrats trying to appeal to people's emotions," he said. "On the other hand, people see President Bush as a man of great principle."

When Bush announced his decision in August 2001, administration officials predicted $100 million would be spent on research involving 78 cell lines. To date, only 20 lines have materialized and a little more than $25 million has been invested. But with thousands of embryos likely to be discarded by fertility clinics, scientists are clamoring to work on some of those.

Lefkowitz said there is nothing stopping private stem cell research. The central issue "is not whether we should permit American society to push the envelope of stem cell research by destroying more embryos," he said, "but rather whether we should use taxpayer dollars for such research."

Castle, a proponent of expanding stem cell research beyond the Bush policy, believes the president can rightly defend his position on moral grounds. If that fails, he added, "the White House hopefully will look at this and move further."

Ronald Prescott Reagan is an outspoken supporter of stem cell research.