Two Republican senators rose to President Bush's defense yesterday on the emotional issue of stem cell research, although both said they are pushing the White House to embrace an expansion of the policy advocated by Democratic presidential nominee John F. Kerry.

At a time when polls show overwhelming support for the research, Sens. Gordon Smith (Ore.) and Trent Lott (Miss.) expressed concern that Bush is not receiving his due for allowing some federally funded research to go forward while Kerry is not being properly scrutinized for supporting the more controversial "therapeutic" cloning. That involves creating a cloned embryo for the sole purpose of research.

In accusing Kerry of "demagoguing" the issue, the pair entered a fray that has caused a public rift in the family of former president Ronald Reagan and prompted first lady Laura Bush to make a rare foray into public policy. And the fight will continue: Republicans announced yesterday that Michael Reagan, who calls embryonic stem cell research "junk science," will speak at the national convention in New York. His brother, Ron Reagan, spoke in support of that research at the Democratic National Convention last month.

"No matter what office you are running for, you are going to get asked the question of where you stand on the issue," said Michael Manganiello, senior vice president of the Christopher Reeve Paralysis Foundation. "It behooves our politicians to be informed on this."

Typically, science does not take center stage in national campaigns. But in a tight race, pollsters say the promise of stem cell research to treat and cure many illnesses is one of the few that could move moderate Republicans and independents.

A recent Zogby International poll found that one of every five Bush supporters would consider switching to Kerry if he were to announce "a major initiative in stem cell research."

Three years ago, Bush decided to allow federal funding on a limited number of cell "lines" derived from 5-day-old human embryos. Although he put no restrictions on private research, many scientists say the 20 or so lines eligible for public money are nowhere near enough to aggressively pursue treatments for illnesses such as Parkinson's, juvenile diabetes and multiple sclerosis.

Still, Lott said: "I do think the president was not getting the credit he deserved."

To illustrate the potency of the issue, Kerry or his surrogates have raised the subject every day since his Saturday radio address, and it was mentioned more than 20 times from the stage of the Democratic convention last month, including the prime-time speech by Reagan. In doing so, the Kerry team hopes to suggest a broader critique of the president as a leader who permits ideological concerns to interfere with science.

"What if we have a president who believes in science, so we can unleash the wonders of discovery like stem cell research to treat illness and save millions of lives?" Kerry said at the convention.

In response, Bush aides this week put out Health and Human Services Secretary Tommy G. Thompson, former domestic policy adviser Jay Lefkowitz, several lawmakers and the first lady.

"We don't even know that stem cell research will provide cures for anything -- much less that it's very close" to providing cures, she said, chastising Kerry's criticism of her husband's policy as "ridiculous."

Smith and Lott said they participated in a Bush-Cheney campaign conference call because of personal experience and political concerns. Lott's grandson is the result of in vitro fertilization, and Smith and his wife failed to conceive using the procedure. Their "created embryos never turned into life," Smith said, but he wants to see "spare" embryos used to benefit science.

As part of the counterattack, Republicans are trying to shift the focus to Kerry's support of therapeutic cloning. Although he distinguishes between a living embryo in a woman's womb and cells in a laboratory, Smith said he nevertheless opposes cloning for research purposes because there is "little way to stop us from going down the path of creating laboratory body farms."

Ron Reagan, in response to Laura Bush, wrote in yesterday's New York Times: "If destroying even an artificially created 'embryo' in a petri dish is equivalent to murder, then I would expect the White House to campaign vigorously against in vitro fertilization clinics that routinely dispose of unneeded early-stage embryos by the thousands."

Michael Reagan has referred to embryonic stem cell research as "junk science."Brother Ron Reagan spoke in favor of such research at the Democratic convention.