The day began with a bang, when Specter, whose support for abortion rights is well known, delved straight into that topic, pressing Roberts on questions of precedent and the legal principle of stare decisis, a Latin term that means "to stand by things decided."

Specter quickly introduced the only prop of the day, a large chart that, he said, demonstrated that the Supreme Court had the opportunity to overrule Roe v. Wade on 38 occasions and had not done so.

He reminded the nominee of a remark that Roberts made in 2003, when the Senate was considering him for the seat he has on the U.S. Court of Appeals for the District of Columbia Circuit, in which he said Roe was "settled law."

"Do you mean settled for you?" Specter asked. "Settled only for your capacity as a circuit judge? Or settled beyond that?"

"Well, beyond that," Roberts replied. "It's settled as a precedent of the court, entitled to respect under principles of stare decisis."

Both conservatives and liberals said afterward that the line of questioning was smart strategy on Specter's part. "I think it takes some of the wind out of the Democrats' sails later," said Leonard Leo, who has taken leave from his job at the Federalist Society, a conservative legal group, to coordinate support for Roberts.

Some of the most freewheeling exchanges of the day involved Biden, a potential presidential candidate, who elicited from the nominee that there is a right to privacy to be found in the 14th Amendment's liberty clause and that the right extends to women.

The comment was important because the right to privacy provided a part of the philosophical underpinning for Roe. But Roberts was careful as he made the remark, telling the senators that all the current Supreme Court justices would agree that there is a right to privacy "to some extent or another."