Specter's remarks suggested he did not believe Roberts would inject personal views into his judicial rulings, a comment of potential political significance coming from a senior Republican who has long supported abortion rights.

It marked the second time in two days that Roberts' nomination was boosted by Republican senators known for reaching across party lines. On Wednesday, John McCain, R-Ariz., said Roberts did not meet the definition of "extraordinary circumstances" that would justify a filibuster under a compromise worked out by 14 senators earlier this spring.

While Senate Democrats generally have declined to express positions on Roberts' nomination, there were expressions of praise from some among the group involved in this spring's compromise.

Ben Nelson, D-Neb., said Bush had made a "wise choice." Said Sen. Mark Pryor of Arkansas, "So far, so good."

Some abortion rights organizations have announced their opposition, expressing fears Roberts will become part of a court majority that first erodes and eventually overturns the historic 1973 ruling.

NARAL Pro-Choice America has cited a legal brief he co-authored for a Supreme Court case while serving as deputy solicitor general in the administration of the first President Bush. "Roe was wrongly decided and should be overruled," it said in part.

Asked about the legal filing, 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," he said at the time.

Specter, too, said he intended to pursue the issue.

"Now I don't know if that means it's settled for a circuit judge or if it's settled generally, but I intend to look at that," he said. The Pennsylvanian added, though, that he would not ask Roberts whether he would vote to sustain the 1973 ruling if the nominee became a justice.

At the same time, an AP-Ipsos showed that 52 percent of all Americans — and 60 percent of women — want to know Roberts' position on abortion before the Senate votes on his nomination.

The nervousness about Roberts among abortion rights groups has been fueled by his resume. He served in two Republican administrations and was appointed to the appeals court two years ago by Bush. Women's groups aligned with Democrats also point to comments from conservative activists who have praised Roberts' selection.

There is little in Roberts' record to guide partisans on either side of the abortion record.

Even before Bush publicly announced his selection, the White House has worked to assure abortion opponents and other conservatives that he would fulfill their hopes. These activists appear to be acting in part on political faith, however, choosing to accept reassurances from the White House and intermediaries who know Roberts and have vouched for him.