WASHINGTON -- In nearly 35 years on the Supreme Court, Justice John Paul Stevens went from idiosyncratic maverick to the leader of the court's liberal wing. He always described it as the court's evolution more than his own -- almost all of his colleagues, he said, had been replaced by a justice with more conservative views.

The pattern is likely to continue with Stevens' successor.

Whether the court changed or Stevens changed or the political climate changed -- there's evidence of each -- the justice's decision to step down this summer almost certainly will mean a more conservative Supreme Court, even with Barack Obama in the White House and Democrats controlling Congress.

In his time on the court the justice has left a liberal imprint. He embraced affirmative action (after first questioning it); declared a belief that the death penalty is unconstitutional (after first voting to restore it); and supported protections for gays.

He also defended abortion rights and opposed the notion that the Second Amendment guarantees a right to personal gun ownership.

It is questionable whether Obama, in the current political climate, could replace Stevens with a nominee who shares such strong opinions, even if that were the president's inclination. His nomination of Sonia Sotomayor last year made history but wasn't based on ideology. His appointments of lower-court judges, with a few exceptions, are more middle-of-the-road than the left would like.

But a bigger loss for liberals, who already are seeing their victories at the Supreme Court dwindle, will be Stevens' skills at building majorities. And no liberal on the reconstituted court will have the powers of seniority that Stevens, 89, put to use.

As was clear at the beginning of Obama's presidency, the actuarial tables are against him in remaking a newly muscular conservative court into a progressive force. Replacing a conservative justice with a liberal would make a difference, but the four justices consistently on the right are younger and show no signs of departure.

Douglas Kendall, head of the liberal Constitutional Accountability Center, said that makes the stakes higher for Obama this time than they were last year, when he chose Sotomayor to replace retiring Justice David Souter. Souter was a consistent vote on the left but not a leader on the court.

"Replacing Justice Stevens is harder because Stevens plays so many critical roles on the current court: He's the leader of the liberal wing, the best opinion writer on the court and, simultaneously, the justice most able to build surprising coalitions," Kendall said.