WASHINGTON  Representative Henry A. Waxman wrested the chairmanship of the powerful House Energy and Commerce Committee from Representative John D. Dingell on Thursday in a coup that is expected to accelerate passage of energy, climate and health legislation backed by President-elect Barack Obama.

Mr. Waxman, 69, of California, who mounted a quiet but devastatingly effective two-week campaign against his longtime Democratic colleague, won the chairmanship with a 137-to-122 vote in the Democratic Caucus. The vote was secret, but many allies of Speaker Nancy Pelosi backed Mr. Waxman’s move, and several members said they had voted on the assumption that Ms. Pelosi had tacitly approved.

Democrats also read the signals coming from the president-elect’s transition office, which this week announced the intention to name Philip Schiliro, a longtime aide to Mr. Waxman, as the White House director of Congressional relations.

The takeover marked the fall of a third long-serving member of Congress in the last two weeks. Senator Ted Stevens, 85, Republican of Alaska, lost his re-election bid after a federal fraud conviction. Senator Robert C. Byrd, 91, Democrat of West Virginia, stepped aside as chairman of the Senate Appropriations Committee last week.