(CNN) - President Barack Obama received his second opportunity Friday to shape the U.S. Supreme Court when Justice John Paul Stevens announced his retirement.
The president named Judge Sonia Sotomayor to the court last year.
To replace Stevens, Obama is likely to nominate another Democrat, thus maintaining the court's ideological balance of five conservative to four liberal-leaning judges.
Democratic Sen. Arlen Specter of Pennsylvania - a longtime member of the Senate Judiciary Committee, which considers Supreme Court nominees - said recently that he would lobby Obama to choose a successor for Stevens who supports limiting executive power built up during George W. Bush's presidency.
"I think we need someone who will step into Justice Stevens' shoes, who will be very tough on the issues of executive power," Specter said on "Fox News Sunday."
"I think we need the kind of balance that Justice Stevens has provided to offset the majority on the court, which is in favor of executive power."
On the same program, Republican Sen. Jon Kyl of Arizona refused to rule out a GOP filibuster of an Obama nominee to the Supreme Court. Republicans control 41 seats in the Senate, enough to stall the confirmation process, and they are considered likely to win a few more seats in midterm elections in November.
"It will all depend on what kind of a person it is," Kyl said, adding that he disagreed with Specter's call for a nominee with a clear position on an issue such as executive powers.
"I want a judge who will read the law and declare it in each case that comes before him or her as it should be. In other words, don't have somebody coming in with preconceived attitudes - 'I'm going to be tough on the executive,' or, 'I'm going to be for the little guy,' or whatever their preconceived attitudes are," Kyl said.