Miller, 68, is an ally of House Democratic leader Nancy Pelosi, who described him in a statement as a "close friend" and "the model of the serious, substantive and successful legislator."

"I have not won every fight that I have waged," Miller said in his statement. "And there remain, of course, many critical challenges waiting to be addressed. But I have no regrets about what I have accomplished and what I have tried to accomplish in the public interest."

Miller is again trying to boost the minimum wage. He has introduced legislation that would raise it gradually to $10.10 an hour and link future increases to the Consumer Price Index. Democrats say the issue will be key to their election-year focus on reducing income inequality.

"No one would confuse me and George Miller for ideological soul mates," House Speaker John Boehner, an Ohio Republican, said in a statement. "But during our years serving together on the Education and the Workforce Committee, we got things done on behalf of the American people thanks in no small part to his dedication and willingness to work for the greater good."

Born in 1945 and elected in 1974, Miller is one of fewer than 20 lawmakers who have served more than half their lives in the U.S. Congress. While in Washington, he lives in a two- bedroom rowhouse with Senate Democrats Dick Durbin of Illinois and Charles Schumer of New York.

He's one of just two remaining Democrats known as "Watergate babies" of the freshman class elected in 1974, in which 75 Democrats won in the aftermath of the scandal that cost Richard M. Nixon the presidency. The other is Representative Henry Waxman, a California Democrat.