President Bush's signing of a ban on partial-birth abortions (search) helps him shore up re-election support within his party's conservative core. It also appears to be triggering some unintended political consequences, from mobilizing abortion-rights activists, who consider it the first attack on the 1973 Supreme Court (search) ruling that legalized abortion, to setting up a divisive election-year battle over the court's next vacancy.

Given the strong passions surrounding any abortion question, the president's signing of a bill Wednesday that outlaws what critics call partial-birth abortion could have political ramifications far beyond the medical and ethical issues at stake.

While energizing one's political base is important, "the other side of it is you don't want to stir up the base of the opposition," said James Thurber, a political scientist at American University.

"And this stirs up the base of the opposition more than most issues. They are organized, and they will remember this, and they will come out, and it will hurt him," Thurber said.

It didn't take abortion-rights activists long.

As promised, even before the ink from Bush's pen was dry, opponents went to court to challenge the new federal ban and to seek an injunction to keep it from taking effect. A federal judge in Lincoln, Neb., immediately issued a temporary restraining order after a three-hour hearing; the ruling barring the law's enforcement applied only to four doctors.

Many observers — including some of the new law's supporters — doubt that it will be upheld by the current Supreme Court, since it differs little from a Nebraska law struck down by a 5-4 vote in 2000.

Activists also moved to try to turn the issue into a 2004 campaign debate over broader abortion rights.

"George Bush has crossed a line, and we are going to be working hard to make sure every member of America's pro-choice majority understands the significance," said Kate Michelman, president of NARAL Pro-Choice America (search).

Americans are well used to the abortion controversy. It has been raging in one form or another for the three decades since the 1973 Roe v. Wade decision struck down state anti-abortion laws.

But since support for abortion rights crosses party lines, recent GOP presidential nominees, including Bush in 2000, have not sought to emphasize the issue.

The law that Bush signed, similar to ones former President Clinton twice vetoed, bans certain procedures on fetuses that are partially delivered, and then killed. The technique is used during the second and, occasionally, third trimester of pregnancy.

Recent polls show that as many as seven out of 10 Americans think such practices should be illegal. Final passage in the Senate last month was by a lopsided 64-34 vote, with 17 Democrats, including Minority Leader Tom Daschle of South Dakota, supporting the ban.

Bush called the procedure Wednesday "a terrible form of violence ... directed against children who are inches from birth."

Still, the nation remains much more evenly divided on the broader issue of whether the Roe v. Wade decision should remain in force. Bush acknowledged as much last week when he told reporters: "I don't think the culture has changed to the extent that the American people or the Congress would totally ban abortions."

Abortion-rights advocates are using Wednesday's bill-signing to mount a broader campaign.

"What this is about is a direct stab at Roe v. Wade. It's a direct stab to roll back or whittle away at a woman's right to choose," said Rep. Carolyn Maloney, D-N.Y.

Some hard-line Republicans also saw it as a new opportunity to increase pressure on Bush to nominate a strongly anti-abortion candidate for the next Supreme Court vacancy, particularly if it's the seat of Sandra Day O'Connor. Often the swing justice on the nine-member court, she voted with the 5-4 majority in striking down Nebraska's late-term abortion prohibition in 2000.

A pitched battle over a potential Supreme Court vacancy is the last thing Bush's political strategists want to see in the midst of a presidential election campaign.

Strategists in both parties see the 2004 election as likely to be extremely close, one that could be decided in a handful of pivotal states.

An important voting bloc in those states is moderate suburban women, many of whom support abortion rights. It's a group Bush will be actively courting in the general election campaign.

So far, he has carefully tended to the needs of conservatives, recognizing that their active support is necessary for re-election.

But, running unopposed for his party's nomination, Bush already had most of them in his corner anyway.