WASHINGTON -- On Oct. 4, four days before he celebrated his 15th anniversary on the U.S. Supreme Court, Justice David H. Souter could turn on the television to see that his appointment to the court was still controversial.

That was the day President Bush held a news conference to defend his second nominee to the court, White House Counsel Harriet Miers, against complaints that Ms. Miers might turn out to be "Souter in a skirt."

The president joked that by asking him about Justice Souter, reporters were "trying to get me in trouble with my father." But in insisting that Ms. Miers would adhere to her current views "20 years from now," Mr. Bush implicitly endorsed the conventional wisdom on the right that Justice Souter joined the court as a conservative and then morphed into a liberal.

That Justice Souter should be a flashpoint in public debate is ironic.

Although the 66-year-old Harvard- and Oxford-trained jurist is an active questioner at oral arguments and the author of erudite opinions, he is regarded as less influential than his liberal colleagues John Paul Stevens and Stephen Breyer. Outside the court, he has maintained a low profile.

Unlike some of his colleagues, he is scarce on the Washington social circuit and does little public speaking.

More is involved in the demonization of David Souter than his support for legal abortion or gay rights -- positions also held by Justices Sandra Day O'Connor and Anthony Kennedy -- or the fact that, unlike those two Republican appointees, he is a consistent vote for separation of church and state.

Justice Souter owes the opprobrium among conservatives to two articles of faith on the right.

The first is that the former New Hampshire Supreme Court justice was marketed to the first President Bush as a reliable conservative despite his lack of a paper trail on constitutional issues. The second is that once on the court, he switched sides, voting more like the liberal justice he replaced, William J. Brennan Jr., than with Justices O'Connor, Kennedy and Antonin Scalia and Chief Justice William H. Rehnquist.

Mark Tushnet, a law professor at Georgetown University and the author of "A Court Divided: The Rehnquist Court and the Future of Constitutional Law," said both perceptions were rooted in reality.

"Unlike with Kennedy, there was no honeymoon period for conservatives," Mr. Tushnet said. "Souter relatively quickly moved to the left. And there were explicit assurances from [then White House Chief of Staff John] Sununu that Souter was a conservative."

Other students of the court note that Justice Souter's earliest votes might have given the conservatives false hope. Thomas M. Keck, a political scientist at Syracuse University and the author of "The Most Activist Supreme Court in History," has cited several cases in Justice Souter's first days on the court in which he sided with conservatives to uphold police searches, allow the admission of confessions where police had committed "harmless error" and permit prosecutors to introduce "victim impact" evidence at capital sentencing hearings.

Even then, Mr. Keck wrote in an essay, Justice Souter "gave some indication that he would temper the court's conservative approach with a dose of moderation."

In his early years, some commentators saw Justice Souter as part of a "centrist" majority that often included the moderately conservative Justices Kennedy and O'Connor. Exhibit A was the now-famous "joint opinion" in the 1992 case of Planned Parenthood v. Casey in which Justices Souter, Kennedy and O'Connor upheld the "essential holding" of the Roe v. Wade decision legalizing abortion, even as they upheld most provisions of the Pennsylvania Abortion Control Act.

Although all three justices signed the opinion, Justice Souter is widely thought to have written a section emphasizing the need for the court not to "surrender to political pressure" to overturn Roe.

Conservatives were appalled by Planned Parenthood v. Casey, in which, according to Mr. Keck, Justice Souter "helped craft a successful compromise."

That the justice sold to the first Bush administration as a "home run" for conservatism would have spearheaded the survival of Roe v. Wade added to the sense of betrayal.

On other issues, Justice Souter clearly has voted not as a "centrist" but with the court's liberals, including Bill Clinton appointees Breyer and Ruth Bader Ginsburg. He has sided with them not only in taking a strict view of separation of church and state but also in supporting a strong constitutional role for Congress relative to the states. On these "federalism" cases, Justice Souter has found himself on the opposite side from fellow Republican appointees Kennedy and O'Connor.

Among those secondary issues of interest to conservatives is the legal status of homosexuality, and here, too, Justice Souter has voted with liberals (and moderate conservatives like Justices O'Connor and Kennedy) and parted company with Justices Antonin Scalia and Clarence Thomas. Justices Souter, O'Connor and Kennedy all voted to strike down laws against same-sex sodomy in the 2003 case of Lawrence v. Texas.

Mr. Keck said that Justice Souter is now clearly established as a voice of the sort of liberalism that "seeks to enforce those fundamental liberties that are essential to individual human liberty or to democratic governance." But where such principles aren't at stake, Mr. Keck added, Justice Souter believes the court should show "significant deference to the elected branches of government."

This stance makes him the polar opposite of the court's two most conservative members. Justices Scalia and Thomas, who believe the court should be restrained in protecting rights not explicitly granted in the Constitution and aggressive in overturning congressional acts that undermine states' rights."

Mr. Tushnet has described Justice Souter's philosophical journey not as a repudiation of an earlier conservatism on constitutional issues or as the natural culmination of his earlier views but rather as the result of being confronted with issues that never faced him before he joined the court.

In "A Court Divided," Mr. Tushnet notes that the justice once told a law clerk: "I never had to think about these things until I came to Washington. I never thought about them. I had no settled views."

The same, of course, could be said about Harriet Miers.