Court Tuesday after winning Senate confirmation, a personal triumph for the son of an Italian immigrant and a political milestone in President Bush’s campaign to give the judiciary a more conservative cast.

The 58-42 Senate vote was largely along party lines as Democrats registered overwhelming opposition to Bush’s choice to replace Justice Sandra Day O’Connor, whose rulings have helped uphold abortion rights, affirmative action and other legal precedents of the past 50 years.

Bush hailed Alito as “a brilliant and fair-minded judge who strictly interprets the Constitution and laws and does not legislate from the bench.”

“It is a seat that is reserved for few but that impacts millions,” said Senate Majority Leader Bill Frist moments before the Senate sealed Alito’s place in history as the nation’s 110th justice.

Alito, 55 and a veteran of 15 years on the appeals court, watched on television alongside Bush at the White House as the Senate voted.

He was sworn in about an hour later in a low-key ceremony at the Supreme Court building across the street from the Capitol. Chief Justice John Roberts, Bush’s first nominee for the high court, administered the oath of office.

Alito’s confirmation has been a certainty for days, and all Republicans except Sen. Lincoln Chafee of Rhode Island voted for him. Only four of 44 Democrats voted in favor of confirmation, the lowest total in modern history for an opposition party.

“There is no consensus that he will allow the court to perform its vital role in continuing the march of progress toward justice and equal opportunity,” said Sen. Edward M. Kennedy, leader in a final attempt to derail the nomination that exposed Democratic divisions instead.

Roberts was confirmed by a far wider margin, 78-22, late last year, replacing the late William H. Rehnquist.

Republicans were unanimous in voting for Roberts, and Democrats had split evenly, 22 in favor and 22 opposed.

Roberts was viewed by Democrats as one conservative replacing another. By contrast, Alito is seen by Democrats and outside groups aligned with them as a Reagan-era conservative replacement for a moderate justice whose opinions kept the court centered.

The conservative Family Research Council said it welcomed Alito’s confirmation on behalf of those whose “weariness over the court’s embrace of judicial activism rallied voters across the country in pursuit of a new course.”

Apart from placing Roberts and Alito on the nine-member Supreme Court, the Senate has confirmed Bush appointees to 42 of 179 total seats on the federal appeals courts. Several of those were confirmed in bruising political battles that brought the Senate to the verge of political meltdown.

Bush has long said he hoped to appoint members of the Supreme Court in the mold of Justices Antonin Scalia and Clarence Thomas.

The two men are among the court’s minority that has voted to overturn the landmark 1973 court ruling that establish a woman’s right to an abortion, the issue representative of a political and cultural divide that has persisted for over 30 years.

Judging from the court docket, the first case Alito will hear from his seat at the far right end of the bench will involve a pair of challenges to Clean Water Act regulations, appeals from cases filed by landowners and a paper mill.

Alito’s confirmation capped a seven-month drama that began when O’Connor announced she would retire, signaling the first change on the court in a dozen years. Bush named Roberts to replace her, but Rehnquist died before the Senate could hold hearings. The president swiftly tapped Roberts to be chief justice.

Bush then named White House counsel Harriet Miers to the O’Connor seat, but she drew fierce opposition from conservatives who worried that she would not be reliable enough on issues such as abortion. Abandoned by Senate conservatives, she withdrew. Bush picked Alito to replace her, turning to an appeals court judge with unchallenged intelligence and sterling conservative credentials.

Alito graduated from Princeton and Yale Law School, then worked as a federal prosecutor in New Jersey. He held two positions in the Reagan administration over a period of several years, and in 1985, seeking a promotion, he wrote a memo that became the basis for Democratic opposition to his nomination.

In it, he said there was no constitutional right to an abortion. He reinforced the view after he won the job, writing a legal memo suggesting the Justice Department try to chip away at abortion rights rather than mount an all-out assault.

Alito walked into his confirmation hearings with all the support he needed among majority Republicans, and no evident backers among Democrats. Little changed in the intervening days, as Democrats challenged him on his views and attacked him for his membership in a conservative Princeton Alumni organization and for his decision to rule in a case involving a company in which he held investments, despite a 15-year-old promise not to.

Alito’s wife, Martha-Ann Bomgardner, left the hearing room in tears near the end of one contentious session, the defining moment of the proceedings – and one that left Democrats conceding the nomination was unstoppable.

Even so, Kennedy and Sen. John Kerry announced late last week they would try to block a final vote. Their move was crushed, 75-25, with 19 Democrats joining Republicans to approve a Monday test vote.