Kerry on Saturday criticized Bush for a "far-reaching ban on stem-cell research," which the Massachusetts senator said shut down promising work to fight Alzheimer's, Parkinson's, diabetes and AIDS.

"At this very moment, some of the most pioneering cures and treatments are right at our fingertips, but because of the stem cell ban, they remain beyond our reach," Kerry said in a radio address.

First Lady Laura Bush shot back on Monday, calling Kerry's claim "ridiculous."

"We don't even know that stem cell research will provide cures for anything—much less that it's very close," she said in an interview with the Associated Press.

She also said it is inaccurate to portray the president's order limiting research as a ban. "That's so ridiculous," the first lady said. "It's one of the myths that start during a campaign."

Noting that her own father died of Alzheimer's, Mrs. Bush told the Pennsylvania Medical Society that suggesting a cure for such diseases is just around the corner is "really not fair to the people who are watching a loved one suffer with this," according to Reuters.

Kerry's running mate, Sen. John Edwards of North Carolina, described Monday--the three-year anniversary of President Bush's limiting of federal funding of research to the 78 stem cell lines that existed in 2001--as "a sad anniversary."

Edwards said the Kerry campaign is "committed to scientific research based on fact, not ideology" and pledged if elected to increase funding for embryonic stem cell research at the National Institutes of Health, encouraging young scientists to enter the field, while putting in place strict ethical standards.

White House spokesman Scott McClellan on Monday said the president would not expand his decision and open addition cell lines for research. While Bush was the first president to authorize federal funds to explore the potential of embryonic stem cell research, McClellan said the president believes "it is important that we not go down a dangerous slippery slope where we divorce science from ethics."

The issue entered the current election debate when Ron Reagan, son of former President Ronald Reagan, who died in June from complications of Alzheimer's, touted potential of stem cell research at the Democratic National Convention.

Reagan said some oppose the research, arguing destruction of a fetus, even if it will never be implanted in a womb, is tantamount to murder.

"A few of these folks, needless to say, are just grinding a political axe and they should be ashamed of themselves," Reagan said. "But many … are well-meaning and sincere. Their belief is just that, an article of faith, and they are entitled to it. But it does not follow that the theology of a few should be allowed to forestall the health and well-being of the many."

Leaders on the religious right reacted strongly.

"The Democrats want Americans to think that if you oppose embryonic stem cell research you must be a right-wing whacko with 'an axe to grind,'" said Jerry Falwell in his July 29 "Falwell Confidential" column on Falwell.com.

Richard Land of the Southern Baptist Convention compared Reagan's argument to thinking of the Third Reich. "What Ron Reagan is calling ignorance is called civilization," Land, president of the SBC Ethics & Religious Liberty Commission, said in Baptist Press.

Democrats hope the issue will become a wedge issue that prompts undecided voters to come over the Kerry.

An NBC News/Wall Street Journal poll in June found 71 percent of Americans agreed with using for research embryos that would otherwise be discarded.

Andrew Kohut of the Pew Center for the People and the Press said swing voters, while less interested on most issues in the campaign than supporters of either candidate, are actually more interested in the stem cell issue. They also tend to be more moderate, leaning toward research.

Kohut said support for medical research is increasing as people learn more about it. A Pew survey now in the field is showing stronger support for stem cell research than a similar one two years ago, he told NPR.

Many Christian ethicists, however, say the issue is more complex than pitting science against theology.

Dennis Sansom, who teaches in the philosophy department at Samford University, said the debate poses a dilemma between values of "beneficence," or doing good, and respect for human dignity.

Even in its earliest stages, Sansom said in a paper delivered recently to the Baptist World Alliance, the fetus has at least "potential human" dignity, which must be weighed against potential good. For example, while it might be justifiable to kill an embryo for treatment of a catastrophic disease, offering direct benefit, it is morally dubious to do so for research, which is merely potential benefit.

Some argue that existing embryos sitting frozen in fertility labs should be available for research, because most will never be implanted and may eventually be thrown away.

Sansom, however, said he believes for now the only way to follow the rule is to use embryos that are already destroyed, like discarded frozen ones, miscarriages or abortions. Using their stem cells "would partially redeem an unfortunate circumstance," he said in an e-mail to EthicsDaily.com.

"Their dignity in such cases would not be violated by the intention to use their stem cells, but to create them only for their stem cells, even for the good of others, obviously disavows their dignity," Sansom said.

Bob Allen is managing editor of EthicsDaily.com.

Also see Dennis Sansom's column, "The Face of War."