It’s rare that Democrats discover and exploit a “wedge issue” in a political campaign, but they are doing so — gratifyingly, to me — on embryonic stem-cell research. [IMGCAP(1)]

As many readers know, my wife, Milly, died on July 22 of Parkinson’s disease, one of the likeliest diseases to be cured some day through stem-cell research. Because of this, I can’t be unbiased about the fact that Democrats would advance the research and most Republicans would retard it.

Three years ago, President Bush imposed severe limits on federal funding of stem-cell research using embryos “left over” at in-vitro fertilization clinics. He also proposes to ban so-called “therapeutic cloning” of embryos for research purposes, a position shared by GOP leaders in Congress.

On the other hand, Democrat John Kerry vows to lift Bush’s limits and increase federal funding. He would also advance therapeutic cloning. On these issues, the two candidates could not be further apart.

Polls indicate that the public overwhelmingly supports the Kerry position on stem cells — including the Roman Catholics whom President Bush presumably hopes will support him in declaring that embryos, even in a test tube, are “human life.”

I believe that they are potential life. I would not destroy them (or create them) for just any purpose. But to save living human beings from dread diseases? The moral balance has to tilt decisively in that direction.

In the close election that this one figures to be, continued Democratic emphasis on medical research and stem cells could be decisive. Tens of millions of people either suffer from dread diseases or have a loved one who is afflicted.

In July, Catholics for Free Choice published a poll of 2,239 Catholics nationwide — a large sample — and found that 72 percent support “allowing scientists to use stem cells from very early human embryos to find cures for diseases.”

A June NBC News/Wall Street Journal poll showed that, when offered a reasonable summary of the Kerry and Bush positions on the use of fertility clinic embryos, voters split in favor of Kerry’s stance by 71 percent to 22 percent.

Undecided voters split 66-25 for the Kerry position, and “weak Bush” voters split 77-17 that way. Even among “strong Bush” voters, 58 percent favored allowing the research.

A recent Zogby International poll indicated that one in every five Bush supporters would consider switching to Kerry if he were to announce a “major initiative in stem-cell research.” Lately, he has done just that.

In the lead-up to Aug. 9, the third anniversary of Bush’s 2001 decision to limit federal funding of research to stem cells already derived as of that date, the Kerry campaign let fly with a barrage of statements and speeches on the stem-cell issue.

Kerry devoted the Democrats’ weekly radio address to the issue, declaring that “here in America, we don’t sacrifice science for ideology. … People of good will and good sense can resolve the ethical issues without stopping life-saving research.”

Now, biased as I am toward the Kerry position, I have to say that Republicans have a point when they charge that Kerry has hyped, and even demagogued, the issue.

“Stem cells have the power to slow the loss of a grandmother’s memory,” he said, “calm the hand of an uncle with Parkinson’s, save a child from a lifetime of daily insulin shots or permanently lift a best friend from his or her wheelchair.”

On Aug. 10, first lady Laura Bush was correct in saying that while she hopes stem-cell research will produce cures, “I know that embryonic stem-cell research is very preliminary and the implication that cures for Alzheimer’s are around the corner is just not right, and it’s not fair to the people who are watching a loved one suffer from this disease.”

The same applies to Parkinson’s, juvenile diabetes and spinal-cord injuries. Stem cells don’t yet have the “power” to cure these ailments — just the “potential.” Which is why I’d argue, without hyping, that it’s a disastrous mistake to limit the research.

If Kerry is hyping, the Bush administration is indulging in legerdemain of its own. It claims that Bush is the first president ever to fund embryonic stem-cell research. That’s true — but only because it’s a new technology that only became relevant at the end of the Clinton administration.

Shortly before leaving office, the Clinton administration issued a finding that would have permitted full federal funding of research on embryos destined for destruction at in-vitro clinics.

Bush revisited that decision. His policy was not a “ban,” as Democrats charge, but a restriction on funding to what Bush said were nearly 70 previously derived batches, or “lines,” of stem cells. The president’s policy barred funding for research on any newly derived lines. Bush also promised to devote $100 million to the permitted research.

As it turns out, Bush overstated the number of usable “lines” — there are fewer than 20 worldwide — and his administration has devoted only $25 million to the research.

Kerry clearly would do much more. And, if this helps him in the election, good for him.