It's been five years in the making. It pits the promise of life-saving medical advances against the precept that human life – even in its earliest stages – is sacred. And it is poised to produce the first veto of George W. Bush's presidency.
So it is no surprise that the stem-cell debate opening in the Senate Monday has been choreographed as carefully as a classical ballet – all but the ending.
Republican and Democratic leaders have agreed to allow three bills related to stem-cell research to come to the floor of the Senate: 12 hours of debate, no amendments, and votes to start at precisely 3:45 p.m. on Tuesday. In a sign of how high the stakes have become, once the Senate has voted, no other bill or amendment relating to the issue will be allowed for the rest of the 109th Congress.
One bill, which has already passed the House in May 2005, eases the presidential limit on the number of embryonic stem-cell lines that can be used in federally funded research. Another promotes research using other forms of stem cells that do not require destroying human embryos. And a third aims to preempt research on embryos from "fetal farms," where human embryos are created for research.
All three are expected to pass and land on the president's desk this week. Mr. Bush is expected to sign the second two bills into law. But the first one is all but certain to draw his first veto. Then, with nearly 3 in 4 Americans in support of the vetoed bill, the question is: Will the GOP-controlled House and Senate muster the will and the votes to override the veto?
It may be possible for the Senate to reach the 67 votes needed for an override, but it's unlikely in the House, say aides on both sides of the aisle.
"We need 290 votes [to override a presidential veto], and hope springs eternal, but that's a fairly heavy lift," says Rep. Diana DeGette (D) of Colorado, a sponsor of the House bill, who says that a veto would put the ideology of the religious right ahead of the health of millions of Americans. "I am outraged that President Bush is considering using his first veto on legislation that holds the key to helping millions of Americans suffering from diseases like Parkinson's and diabetes," she adds. "This research is far too important to be used as a political wedge."
When Bush approved the first federal funding for scientific research on a limited number of stem-cell lines on Aug. 9, 2001, he called the issue "one of the most profound of our time."
On the one hand, he noted, stem cells appear to have special ability to develop into different cell types, offering hope for breakthrough medical therapies to grow or repair organs and tissue.
But such research also opens the door to moral hazards, he said, such as growing human beings for spare body parts. And he worried about a "culture that devalues life."
Using existing stem-cell lines, created from embryos that had already been destroyed means that no taxpayer dollars would be used to "sanction or encourage further destruction of human embryos that have at least the potential for life," he said.
"[Bush] does not believe we are forced to choose between science and ethics, and with the right policies, we can pursue both," says White House spokesman Ken Lisaius. "A crucial principle is that government should never encourage the destruction of human life."
Democrats see the stem-cell controversy as a political asset.
"This is a bill that every family in America ... is one phone call or one diagnosis away from needing," said House Democratic leader Nancy Pelosi last week. Aides say Democrats will target Republicans who don't vote to override a presidential veto in November elections.
"It's becoming a very significant issue to a group of voters who in the past were not open to us," such as Protestant Republicans who are not evangelical, Sen. Charles Schumer (D) of New York told reporters last week.
On Saturday, Missouri senatorial candidate Claire McCaskill delivered the weekly Democratic radio address on the topic, a key issue in her race to oust freshman GOP Sen. Jim Talent.
The issue has been especially explosive for Senate majority leader Bill Frist. At first, he backed the president's compromise, but announced last year that it was too restrictive. That switch prompted a tongue lashing from antiabortion conservatives.
Since then, Sen. Frist has promoted bills that encourage alternatives to embryonic stem-cell research.
But some scientists and activists are gearing up for ads and press events this week that challenge the claim that alternative stem cells can match the promise of embryonic stem cells.