WASHINGTON – President Bush named federal appeals judge John G. Roberts Jr. to fill the first Supreme Court vacancy in a decade on Tuesday, delighting Republicans and unsettling Democrats by picking a young jurist of impeccably conservative credentials.

If confirmed by the Republican-controlled Senate, the 50-year-old Roberts would succeed retiring Justice Sandra Day O’Connor, long a swing vote on a court divided over abortion, affirmative action, states’ rights and more.

Bush offered Roberts the job in a lunchtime telephone call, then invited him to the White House for a nationally televised, prime-time announcement. The president said his choice will ”strictly apply the Constitution in laws, not legislate from the bench.”

In brief remarks, Roberts said he has argued 39 cases before the Supreme Court in a career as a private attorney and government lawyer. ”I always got a lump in my throat whenever I walked up those marble steps to argue a case before the court, and I don’t think it was just from the nerves,” he said.

”I look forward to the next step in the process before the United States Senate,” he added.

That was a reference to confirmation hearings before the Senate Judiciary Committee, expected to begin in late August or early September. That would allow plenty of time for the Senate to meet Bush’s timetable of a vote before the high court begins its new term on Oct. 3.

Bush administration officials arranged for Roberts to pay his first courtesy calls on leading senators on Wednesday after breakfast with Bush in the White House residence. Republican reaction to the appointment was strongly supportive, while Democrats responded in measured terms.

”I’m just a little surprised that he’s already subject to criticism. But this is America,” said Sen. Arlen Specter, R-Pa., chairman of the Judiciary Committee.

Sen. Edward M. Kennedy, D-Mass., reflecting an emerging Democratic strategy, said he would use the hearings to probe whether Roberts can ”separate his personal ideology from the rule of law.”

Advocacy groups on the left and the right have made plans for multimillion-dollar confirmation campaigns featuring television advertising and grass-roots organizing designed to sway swing vote senators. The ferocity of the battle is undetermined, however.

Abortion – arguably the most politically charged issue to confront Congress and the courts – swiftly emerged as a point of contention.

The abortion rights group NARAL Pro-Choice America announced its opposition to Roberts when word of his appointment leaked before Bush’s formal announcement.

In a written statement, the organization cited a brief Roberts had filed with the Supreme Court while serving as deputy solicitor general in the first Bush administration. In the brief, Roberts said ”Roe was wrongly decided and should be overruled,” referring to Roe v. Wade, the landmark 1973 ruling that established a woman’s right to abortion.

In his defense, Roberts told senators during 2003 confirmation hearings to his current post that he would be guided by legal precedent. ”Roe v. Wade is the settled law of the land. … There is nothing in my personal views that would prevent me from fully and faithfully applying that precedent.”

The National Right to Life Committee, which opposes abortion, countered with a statement of its own. ”Liberal pressure groups will insist that Senate Democrats filibuster against Judge Roberts, unless he pledges in advance to vote against allowing elected legislators to place meaningful limits on abortion,” said the group’s legislative director, Douglas Johnson. ”Millions of Americans will be watching to see if the Democratic senators bow to these demands.”

While he lacks national name recognition, the Harvard-educated Roberts is a Washington insider who has worked over the years at the White House, Justice Department and in private practice.

His professional resume also includes a turn as clerk to William H. Rehnquist, who is 80 and battling thyroid cancer but recently affirmed his intention to remain as chief justice as long as his health allows. It was Rehnquist who presided over the swearing-in ceremony when Roberts took his seat on the appeals court for the District of Columbia.

It took a while for Roberts to get on the bench. He was nominated for the court in 1992 by the first President Bush and again by the president in 2001. The nominations died in the Senate both times. He was renominated in January 2003 and was confirmed by voice vote.

At the time, his nomination to the appellate court attracted support from both sides of the ideological spectrum.

This time, the hearings will be nationally televised, the vote widely watched.

Reaction from Republican senators was strongly supportive. ”He is a brilliant constitutional lawyer with unquestioned integrity,” said Sen. Orrin Hatch, R-Utah.

Majority Leader Bill Frist of Tennessee issued a statement calling for confirmation proceedings that ”treat Judge Roberts with dignity and respect.” Echoing a refrain from this spring’s bitter struggle over Bush’s conservative appeals court nominees, he called for a yes-or-no vote before the court’s term begins Oct 3.

Democratic response was measured, but initially at least, offered no hint of a filibuster.

”The president has chosen someone with suitable legal credentials, but that is not the end of our inquiry,” said Senate Democratic leader Harry Reid of Nevada. Referring to planned hearings in the Senate Judiciary Committee, Reid said, ”I will not prejudge this nomination. I look forward to learning more about Judge Roberts.”

Sen. Dick Durbin, D-Ill., said Democrats would want to probe Roberts’ views to see whether he holds ”mainstream values.”

”He has been a judge for only two years and authored about 40 opinions, only three of which have drawn any dissent,” said Wendy Long, a lawyer representing the conservative Judicial Confirmation Network, adding that his record appears to suit Bush’s desire to nominate a judge who will apply the law, as written, and leave policy decisions to the elected branches of government.

Roberts was one of five prospective nominees Bush met with between Thursday and Saturday, according to a senior administration official who provided details of the selection before the announcement.

This official said Bush’s meeting with Roberts was in the sitting area of the residence so that they could get to know each other in a comfortable setting. The president’s dogs, Barney and Miss Beazley, were under foot.

To meet with Bush and his advisers, Roberts shuttled back and forth across the Atlantic from London, where he was teaching a class.

Bush did not ask Roberts any questions about abortion, gay marriage or other specific issues that might come before the Supreme Court, the official said.

Background on Roberts Age: 50, born in Buffalo, N.Y.

Education: Harvard Law School graduate

Latest Post:· Served on the U.S. Court of Appeals for the District of Columbia Circuit since June 2003

Experience:

· Served as deputy solicitor general during former President Bush’s term

· Argued dozens of cases before the high court What Happens Next?

Selection: The president chooses a nominee who is often vetted by the White House and the Justice Department’s Office of Legal Counsel.

Hearings: The formal nomination is sent to the Senate for consideration. During hearings before the Senate Judiciary Committee, the nominee answers questions, usually about prior court rulings.

Swearing In: The nomination is sent to the Senate for a vote. If confirmed, the new justice is sworn in by the chief justice.