WASHINGTON – In nominating to the Supreme Court a veteran conservative jurist whose legal decisions have touched on virtually every divisive social and political issue in the public square, President Bush has triggered a political battle that could salvage his troubled presidency on a powerful new wave of conservative support.

President Bush’s nomination of a judge from the U.S. Court of Appeals for the 3rd Circuit, Samuel Alito Jr., sparked a backlash from Democratic leaders, who painted the move as an attempt to quell the conservative revolt that helped to derail Mr. Bush’s last nominee, Harriet Miers, and that seemed ready to cost him the support of his strongest supporters.

“If the Miers nomination had gone through, I think that would have been it for President Bush’s support from his base,” the executive vice president of Concerned Women for America, Wendy Wright, said. “Now, people are energized and excited because this is the culmination of what they have been waiting and working for years – a swing vote on the bench who will rule according to the Constitution and not the whim of the elites.”

The conservative support of Judge Alito suggested that Mr. Bush had energized the Republican footsoldiers who helped him win two elections. Their enthusiasm was a possible first step toward recovery for a second term that had become ensnared by scandal, the war in Iraq, and its slow response to Hurricane Katrina.

“This almost presents a kind of judgment day on the court, and the kind of debate you could never have had with Harriet Miers,” a historian of the Supreme Court, Kermit Hall, said. “The lines have been drawn very clearly with this nominee, and I think the erosion of the president’s positions made him vulnerable to this.”

A former Reagan administration lawyer who fought organized and white-collar crime as the U.S. attorney for the District of New Jersey, Judge Alito shares the academic and professional qualifications of Mr. Bush’s first nominee, Judge John Roberts Jr. And Judge Alito’s 15 years on the court make him the most experienced Supreme Court nominee since the Roosevelt administration.

Judge Alito estimated yesterday that he has written more than 300 opinions and has been involved in nearly 4,000 cases while on the federal bench. Democratic lawyers on the Judiciary Committee have begun poring over those cases, and a memo of cases that circulated among Democratic staffers featured six decisions Democrats can be expected to focus on.

Among the rulings Judge Alito will be expected to defend are his partial dissent from a decision that upheld a Pennsylvania law restricting abortion. Citing precedent, Judge Alito argued that in most cases women should notify their spouses before having an abortion. Critics will also focus on a ruling in which he said machine gun ownership is constitutional and a case in which he denied a female police officer’s sexual harassment claims.

“A preliminary review of his record raises real questions about Judge Alito’s judicial philosophy and his commitment to civil rights, workers’ rights, women’s rights, and the rights of the average American which the courts have always looked out for,” Senator Schumer, a Democrat of New York, said. “It’s sad that the president felt he had to pick a nominee likely to divide America instead of a nominee like Sandra Day O’Connor that would unify us.”

Mr. Schumer’s early criticism of Judge Alito was echoed by other Democrats. Senator Clinton, of New York, said Judge Alito’s record “raises serious questions about whether he will be steadfast in protecting our most fundamental rights.”

Asked if he envisions a Democratic filibuster, Mr. Schumer said, “Every thing is on the table.” Yet a number of Democrats from states that voted for Mr. Bush last year issued statements urging a wait-and-see approach.

A filibuster is fraught with political dangers for both sides. Democrats would risk losing the support of the public by blocking a nominee that even fellow party members have described as competent and even-tempered. By prompting a filibuster, Republicans could risk defections within their party. Republicans have a five vote majority and could lose as many as five votes over a filibuster fight. Democrats could lose senators of their own, however, potentially leading to the embarrassment of losing a fight they provoked.

Conservatives showed signs they are eager for a fight, in conference calls and a wave of statements of support. Representatives from groups like the Judicial Confirmation Network, which was silent during the Miers nomination, emerged as supporters of Judge Alito because of what they described as his record of judicial restraint.

“President Bush’s Supreme Court announcement today of Judge Samuel Alito to replace Sandra Day O’Connor was music to the ears of conservatives all across America,” the president of the American Values Coalition, Gary Bauer, said. “And it’s a very bad day for Senate leftists who will be pressured by radical special interest groups to try to ‘Bork’ this nominee.”

Judge Alito’s confirmation would result in the first majority-Catholic Supreme Court in American history. Other Catholics on the court include Justice Scalia, Justice Kennedy, Justice Thomas, and Chief Justice Roberts. Mr. Hall, however, said such a shift would likely mean more to commentators than it would to the outcome of cases.

“It will provide commentators on the court, in light of the abortion issue, an opportunity to suggest that religion will come to play an important role in what the court does on abortion and issues of death and dying,” Mr. Hall said. “But I think that, in the end, other than the political framework in which the justices are likely to be set, the work of the court will not be explained by the religious views of the justices. That would turn out to be a historical first.”

The Associated Press reported that Judge Alito’s 90-year-old mother, Rose, said in an interview: “Of course he’s against abortion.”

Democrats who hope to damage Judge Alito ahead of his confirmation hearing will have to account for the unanimous support he received from a Democratic Senate during his 1990 confirmation for the federal bench. They will also have to counter supportive statements by Democrats, both then and now. The liberal former chief judge for the Philadelphia based 3rd Circuit Court, Judge Becker, described Judge Alito as intelligent and non-ideological.

“I think he’s a fine appointment,” Judge Becker said. “He’s a first-class intellect, a decent human being, and a mensch. He’s brilliant, he’s fair, and very open-minded. I’ve never known him to have an agenda, and he decides every case on the merits, the facts, and the law. He doesn’t decide any more than he has to – doesn’t reach out for issues, and that’s good. He’s just a good, solid legal scholar who writes well and clearly, a real good judge.”