WASHINGTON (AP) - When the Bush presidency ends, opponents of embryonic stem cell research will face a new political reality that many feel powerless to stop.

President-elect Barack Obama is expected to lift restrictions on federal money for such research. House Speaker Nancy Pelosi, D-Calif., also has expressed interest in going ahead with legislation in the first 100 days of the new Congress if it still is necessary to set up a regulatory framework.

"We may lose it, but we're going to continually fight it and offer the ethical alternative," said Rep. Joe Pitts, R-Pa. "I don't know what the votes will be in the new Congress ... but it's very possible we could lose this thing."

Stem cells are the building blocks that turn into different kinds of tissue. Embryonic stem cells,e unlike more mature versions, are blank slates. If scientists could control them, they could direct regenerative therapy, perhaps allowing a diabetic's pancreas to begin produce insulin, for example.

Harvesting stem cells from four- or five-day-old embryos kills the embryo, which outrages opponents of this type of research. But supporters say hundreds of thousands of embryos stored in fertility clinics eventually will be destroyed anyway and that people should be allowed to donate them for research that could help others.

"I believe that it is ethical to use these extra embryos for research that could save lives when they are freely donated for that express purpose," Obama wrote during the campaign in response to 14 questions from scientists, doctors and engineers.

Under President George W. Bush, federal money for research on human embryonic stems cells was limited to those stem cell lines, or families of constantly dividing cells, that were created before Aug. 9, 2001. No federal dollars could be used on research with cell lines from embryos destroyed from that point forward. Federal regulations do not restrict embryonic stem cell research using state or private funds.

John Podesta, head of Obama's transition team, strongly hinted that the president-elect would deal with stem cell research soon after taking office Jan. 20. "As you know, he has said something specific about stem cell research, so I think you can expect that what he said in the campaign will be fulfilled once in office," Podesta said.

Obama made it clear during the campaign he would overturn Bush's directive.

"As president, I will lift the current administration's ban on federal funding of research on embryonic stem cell lines created after August 9, 2001, through executive order, and I will ensure that all research on stem cells is conducted ethically and with rigorous oversight," he said.

Opponents of such research say they will press their case on several fronts.

The main argument is that life begins at conception - that once fertilization occurred in the lab, so did a human being.

Secondly, they will argue that scientists are having success using other methods - adult stem cells that form specific tissues, or reprogramming skin cells to act like stem cells - so money should be directed where the biggest scientific breakthroughs have occurred. For example, this past week, doctors gave a woman a new windpipe with tissue grown from her own stem cells, eliminating the need for anti-rejection drugs.

"We still intend to try and talk about the real facts that it's the adult stem cells providing the actual treatments," said David Prentice, senior fellow at the Family Research Council.

Added Wendy Wright, president of Concerned Women for America: "There's a lot that's happened over the seven years that includes some remarkable scientific discoveries, which really should have made the issue of federal funding of embryonic stem cell research moot."

But Sean Tipton, director of public affairs at the American Society for Reproductive Medicine, took aim at those arguments.

"It's a little disingenuous for opponents who have effectively blocked federal funding of the work to then cite a lack of progress," Tipton said. "You hold someone at the starting line then you criticize them for not getting very far."

Dr. Chi Dang, professor of medicine at the Johns Hopkins University School of Medicine, agreed there have been tremendous advances with adult stem cells. But he said it is not yet clear that they have enough flexibility to be used in all the ways that an embryonic stem cell could be.

"From a scientific viewpoint, we would be cornering ourselves into generalizing things that may not be true," Dang said.

Dang also said these embryos would otherwise be discarded.

"The question is: Is it ethically more acceptable to destroy these embryos by pouring acid on them, or do you deploy these clusters of cells to create new cell lines that could benefit us in the future?"

Samuel Pfaff, a professor at the Salk Institute for Biologic Studies, said he also supports greater embryonic stem cell research to understand what makes them so special that scientists can endow other cells with similar properties.

"I think it's very fair to say that the long-term trajectory for this area of science is to understand embryonic stem cells so well that we don't have to use them anymore." Pfaff said.

On the Net:

Stem cell information at the National Institutes of Health: http://stemcells.nih.gov/info/basics

Candidates answers on embryonic stem cell research: http://www.sciencedebate2008.com