WASHINGTON - President Bush is facing a decision on what his aides call the most sensitive issue of his presidency so far: whether to back federal funding for research on stem cells derived from human embryos - a new area that scientists say could yield treatments and cures for a host of diseases.
There are no clearly defined political sides, as there have been in most abortion-related debates. In fact, there is impassioned disagreement within the Republican Party, within the Roman Catholic Church and even within anti-abortion ranks and Bush's innermost circle.
And there are emotionally wrenching life-and-death dramas on both sides of the issue, some of them involving people close to Bush.
"This will really be a defining moment for this president and this administration," says Daniel Perry, executive director of the Alliance for Aging Research, an advocacy group that supports embryonic stem-cell research. "You can figuratively hear a pin drop with everyone waiting for the White House to clarify its position on this issue."
In stem cells derived from surplus embryos frozen at fertility clinics, research advocates see potential cures for diabetes, Parkinson's, Alzheimer's and other debilitating diseases. Opponents see nothing less than a human life that should not have been destroyed.
Bush is expected to announce within days or weeks whether the government will fund research into embryonic stem cells, the master cells that are the building blocks of the body's tissue and organs.
Embryonic stem cells, isolated by researchers at the Johns Hopkins University and the University of Wisconsin at Madison in 1998, are thought to hold limitless promise. They have the ability to reproduce into any of the body's cell types, such as brain cells, liver cells, nerve cells, insulin-producing cells or heart muscle cells.
Researchers hope they will one day be able to repair diseased or destroyed organs or tissue by transplanting these healthy stem cells into sick patients.
But because embryos must be destroyed to extract the stem cells, some anti-abortion forces see the research as tantamount to murder. They argue that the same science can be conducted using adult stem cells.
Many medical researchers, though, have said it is not clear that adult stem cells are as malleable, and thus as valuable, as those culled from embryos.
The president is confronting not only a moral and religious dilemma - with conservative religious leaders pitted against the medical research community - but a thorny political one as well.
Polls show that the public backs embryonic stem-cell research by a 3-to-1 margin, with support just as strong among Catholics. And even some of those who oppose abortion - including Bush's secretary of health and human services, Tommy G. Thompson - favor such research.
But the president's chief political aide, Karl Rove, is said to be staunchly opposed to the research, for fear of alienating Bush's conservative base and, in particular, Catholic leaders who have been outspoken in their opposition and who could eventually dampen Catholic support for Bush.
Rove has urged Bush to woo the traditionally Democratic Catholic vote, believing it could be a vital swing vote in 2004. Yesterday, for example, Bush honored the late Cardinal John J. O'Connor at St. Patrick's Cathedral in New York, and the president has scheduled a visit with Pope John Paul II this month in Rome.
"This is the type of call that would defy King Solomon's ability," Marshall Wittmann, a conservative analyst at the Hudson Institute, said of the decision facing Bush.
"It is the ultimate test of Bush's political acumen. It is the dilemma of his political strategy - relying on one's base when one lost the popular vote. Either he swims against the tide of popular opinion or he betrays his base."
During the presidential campaign and in his early days in the White House, Bush said he did not think that public money should be spent on embryonic stem-cell research, and he appeared ready to impose a ban on such funding.
The Clinton administration got around a congressional ban on federally funded research on human embryos by allowing the government to fund research on the stem cells - so long as private money alone was used to harvest the cells from the embryos.
As Bush was reviewing whether to overturn the Clinton policy, those who favor the research, including Thompson, took the opportunity to mount an aggressive and personal campaign to try to change the president's mind.
Most remarkable about their public relations drive has been the outspoken backing from anti-abortion conservatives. Sen. Orrin G. Hatch, a Utah Republican, wrote a letter to Bush, insisting that "proceeding with this research is in the best interests of the American public and is consistent with our shared pro-life, pro-family values."