Unlike several other possible candidates to succeed retiring Supreme Court Justice John Paul Stevens, U.S. Court of Appeals Judge Merrick B. Garland probably won't face conservative opposition. Instead, it could be liberals lining up against him.

A small but vocal group of activists is privately saying that Garland is not liberal enough to replace the legendary Stevens, whose opinions defended gay rights and abortion rights and opposed the death penalty. They say Garland is a centrist who won't champion liberal concerns, too often finds middle ground with his conservative colleagues on the Court of Appeals for the District of Columbia Circuit, and showed great deference to President George W. Bush's indefinite detentions at Guantanamo Bay, Cuba.

Herman Schwartz, an American University law professor and the author of several books on the Supreme Court and conservative judicial activism, said he found Garland's early acceptance of Bush's Guantanamo Bay policy "very troubling."

"It meant that nothing that happened to those prisoners -- whether it was abusing them or holding them indefinitely -- would ever be subject to the rule of law," Schwartz said. "For the executive branch to have that kind of power over a person is unconscionable. And for a judge to accept the total irrelevance of the rule of law is a betrayal of that judge's obligation to uphold the Constitution and this nation's ideals."

Garland declined a request for comment.

Even his naysayers acknowledge that he is well liked by progressives and conservatives as a consensus-building judge and for his work as a top prosecutor on the Oklahoma City bombing. Many agree that he might provide the White House with the smoothest political sailing in confirmation hearings.

Among his friends are some of the capital's most powerful Democratic operatives, as well as conservatives such as Chief Justice John G. Roberts Jr. and D.C. Circuit colleagues Laurence H. Silberman and David Sentelle. Some of the conservative judges, Republican sources say, have quietly sent their GOP friends a message: Don't attack Garland.

If conservatives were choosing a nominee, Garland "would be nowhere on the list," said Ed Whelan, president of the conservative Ethics and Public Policy Center, but Garland compares favorably with other candidates President Obama might consider.

"He's earned the respect of a range of folks, including conservatives, and I think he is the most likely to exercise judicial restraint," Whelan said.

Doug Kendall, president of the progressive Constitutional Accountability Center, said his group has not endorsed a candidate, but he called Garland a "brilliant" judge and said progressives could heartily support him for the high court. He said Garland has impressed fellow judges with clear writing and a focus on facts, and hence persuaded many conservatives to join him in sensitive decisions -- a valuable skill for a justice.

"He's won the admiration of everyone around him by taking the job of a judge seriously and engaging in conversation with his colleagues, rather than confrontation," Kendall said.

In criticizing Garland, some liberals point to his decisions in Guantanamo cases. In 2003, Garland sided with two conservatives in a three-judge opinion that dismissed some Kuwaiti detainees' claims that they should be able to cite lack of evidence and challenge their imprisonment at the U.S. military base.