The House's longstanding tradition of seniority took a big hit today when California Rep. Henry Waxman dethroned Michigan Rep. John Dingell from his seat atop the Energy and Commerce Committee. Waxman, a youthful 69, knocked off Dingell, 82, by a 137-122 vote. Ever since Dingell started chairing the committee in 1981, it has taken a sympathetic stance toward Detroit, and focused less on environmental and health care issues. Waxman's challenge to Dingell has created a rift in the Democratic caucus, forcing members to choose between the two House vets. Waxman's victory was also a win for House Speaker Nancy Pelosi, who helped him with his behind-the-scenes campaign to take over the post.