WASHINGTON, July 2 — President Bush’s decision to commute the sentence of I. Lewis Libby Jr. was the act of a liberated man — a leader who knows that, with 18 months left in the Oval Office and only a dwindling band of conservatives still behind him, he might as well do what he wants.

The decision is a sharp departure for Mr. Bush. In determining whether to invoke his powers of clemency, the president typically relies on formal advice from lawyers at the Justice Department.

But the Libby case, featuring a loyal aide to Vice President Dick Cheney who was the architect and chief defender of the administration’s most controversial foreign policy decision, the war in Iraq, was not just any clemency case. It came to symbolize an unpopular war and the administration’s penchant for secrecy.

Even as he publicly declined to comment on the case, Mr. Bush had privately told his aides that he believed Mr. Libby’s sentence, to 30 months in prison, was too harsh.