WASHINGTON — In the final presidential debate, John McCain reaffirmed his support for federal funding of embryonic stem-cell research. In the final weeks leading up to the election, both campaigns released radio ads supporting stem-cell research.

But McCain and Barack Obama differ on issues such as cloning.

McCain did oppose embryonic stem-cell research as late as February 2000, when he, along with 19 other senators, asked the National Institutes of Health to reconsider their proposed funding for embryonic stem-cell research.

But he later reversed his position, and in 2004, he was one of 14 congressional Republicans who sent a letter to President Bush asking him to reverse his policy withholding federal funding from research on embryonic stem-cell lines created after Aug. 9, 2001.

According to a statement published on his website, “Addressing the Moral Concerns of Advanced Technology,” McCain believes that stem-cell research “offers tremendous hope for those suffering from a variety of deadly diseases — hope for both cures and life-extending treatments.”

This past summer, during a presidential forum at Rick Warren’s Saddleback Church in California, McCain said he was optimistic that promising research in adult stem-cell research might make the debate over embryonic stem cells irrelevant.

And such options are surging ahead. A team of Wisconsin researchers said recently that more than 800 labs have begun using an approach they discovered last year: genetically reprogramming adult skin cells to act like stem cells. Part of that team is James Thomson, the University of Wisconsin researcher who first discovered embryonic stem cells in 1998.

Obama, on his website, similarly champions embryonic stem-cell research, heralding its potential to provide “new insights into human development and disease” and promising to advance “this important new field” if elected.

An Obama campaign ad in September claimed that McCain “has stood in the way. He’s opposed stem-cell research ... John McCain doesn’t understand that medical research benefiting millions shouldn’t be held hostage by the political views of a few.”

In a Sept. 24 interview with the scientific journal Nature, Obama pledged to lift the Bush administration’s policy by executive order, allowing federal funding for research on embryonic stem-cell lines.

McCain has made no such promise, although he has criticized the Bush policy. In 2006 and 2007, both senators voted for legislation that would have lifted the funding restrictions.

Proponents of embryonic stem-cell research are hopeful that either candidate would lift Bush’s funding restrictions. “We hope that either [Obama or McCain] will put science and medicine ahead of politics and lift the current virtual ban on federally funded embryonic stem-cell research,” said B.D. Colen, spokesman for the Harvard Stem Cell Institute. “Despite advances in other areas, there is general agreement here that it is essential to continue embryonic stem-cell research.”

Human Cloning

While the candidates have both expressed the belief that “surplus” frozen embryos from in vitro fertilization clinics should be made available for federally funded research, McCain and Obama diverge on the issue of so-called “therapeutic cloning,” also known as somatic cell nuclear transfer. McCain is a co-sponsor of the human cloning ban introduced by Sen. Sam Brownback, R-Kan., for which the U.S. Conference of Catholic Bishops has voiced its support.

“McCain opposes, and Obama supports, legislation to authorize and fund the creation of human embryos by cloning for purposes of research and the production of stem-cell lines,” said Robert George, McCormick Professor of Jurisprudence at Princeton University and member of the President’s Council on Bioethics. “If this legislation passes, the number of embryos created and destroyed using taxpayer money would be massive.”

Nicole Ficere Callahan is based

in Durham, North Carolina.