Powell, 47, whose father held the seat until Rangel beat him in a primary almost 40 years ago, has been an assemblyman since 2000 and was a city councilman from 1992 to 1997.
Powell said he's an independent Democrat. "We need a voice that represents all of the people, not a voice that represents just the political hacks and the political clubhouses."
"Despite the congressman's long history and legacy it's time to turn the page," Powell said. "Everybody knows the change is coming. The question is when and who."
Rangel, 79, also a Democrat, is running for another term. He was first elected to the House in 1970, defeating Rep. Adam Clayton Powell Jr., who had been a pastor and civil rights leader. Powell was dogged by scandal later in his career, accused of misappropriating congressional funds. He retired to Bimini and died in 1972.
Rangel surrendered the chairmanship of the tax-writing Ways and Means Committee last month after being admonished for breaking House rules by accepting corporate-financed travel. He said his exile was temporary.
Powell IV last month was convicted of driving while impaired, a violation, by a Manhattan jury and acquitted of the more serious misdemeanor charge of driving while intoxicated in the 2008 traffic stop. He was fined $300. He said he was neither intoxicated nor impaired, having had only two drinks over several hours.
Rangel launched his campaign two weeks ago at the Alhambra Ballroom in Harlem. Supporters said more than 500 people turned out, including Gov. David Paterson and Manhattan Borough President Scott Stringer, as well as former Mayor David Dinkins and former State Comptroller H. Carl McCall, all with connections to the political community there.
"This is a celebration, not so much for me but for all of us because God has allowed us to be alive for such dramatic changes in our country," Rangel said, citing Barack Obama's election as the first African American president and enactment of health care reform.
The elder Powell was New York's first black congressman starting in 1945. He had succeeded his own father earlier as pastor of Abyssinian Baptist Church and pushed campaigns for jobs and against discrimination.