He said yesterday that he wanted a vacation after nearly nine years, and he might explore opportunities in television, business or politics.
"Kweisi's capable of doing anything he wants to do, whenever he wants to do it," said Arthur Murphy, a longtime Baltimore political consultant. "He's an incredible American success story."
But others wondered whether the entire story of his departure has yet to be told, particularly given long-standing tensions among the group's top leadership.
"I don't buy any of these public pronouncements," said Michael Meyers, president of the New York Civil Rights Coalition and a former assistant director of the National Association for the Advancement of Colored People.
Mfume, 56, announced his resignation during a news conference yesterday at the NAACP's Baltimore headquarters. He said he had no specific plans other than taking "a break" and spending time with his children, in particular his youngest son, who is 14 and in his first year of high school.
In 1996, when Mfume took over the organization, it was $3.2 million in debt and reeling from a sex scandal involving then-Executive Director Benjamin F. Chavis Jr. and a female NAACP employee, Mary E. Stansel. Eight months later, the organization announced that the debt had been erased through fund raising and fiscal austerity.
"Kweisi had an absolutely extraordinary run for which we remain indebted to him," said Francisco L. Borges, treasurer for the national organization. "This is a guy who was not driven by economics but a desire to serve. It would not surprise me if he would go on serving in another capacity."
Mfume, whose annual salary reached almost $300,000, said yesterday that the NAACP has $15 million in reserves.
But the organization's successes have not come without trouble, especially in recent months.
NAACP board members had not resolved issues related to his contract, which expired in October. Also, the Internal Revenue Service began reviewing the organization's tax-exempt status after Mfume and Julian Bond, the NAACP's board chairman, criticized the Bush administration last summer.
Moreover, some have said the relationship between Mfume and Bond had long been strained.
Mfume and Bond denied that any of those issues prompted the resignation. "This is not about some internal squabble," Mfume said.
The articulate and charismatic leader of the nation's oldest civil rights organization reportedly has long been eyeing the seat of Maryland's senior U.S. senator, Paul S. Sarbanes, 71. Political observers also see Mfume as a potential running mate for a Democratic gubernatorial candidate.
Mfume said he did not resign to seek political office, but he did not rule it out. "It really is not about me looking for another office to run for," Mfume said. "If that happens, it happens."
But even before Mfume's resignation, his friends and political allies said he was pondering a run for the Senate. Mfume resigned his House seat in 1996, but he maintains his old campaign committee, which has fueled speculation about a political comeback. The committee had $99,384 at the end of September, according to Federal Election Commission records.
But many political observers say it seems unlikely that Mfume would run for Senate unless Sarbanes decided not to run again - a question that remains unanswered.
But Leggett said he believes that Mfume would make a strong candidate for statewide office or the U.S. Senate. In addition, the Democrats are looking for African-American candidates for the 2006 state elections after the Republicans successfully ran a black candidate for lieutenant governor.
Sarbanes' seat, which comes up for re-election in 2006, has long been a topic for parlor gossip in Maryland politics. The low-key and erudite Democrat has often been rumored to be leaving the Senate. But he has repeatedly foiled an array of political aspirants, returning to office with wide vote margins.
In 1997, then-Mayor Kurt L. Schmoke announced he would make a bid for the U.S. Senate if Sarbanes stepped down. But instead of retiring, Sarbanes went on to easily win a fifth term in 2000.
Yesterday, the senator's spokesman, Jesse Jacobs, said Sarbanes typically does not make a formal political announcement until much closer to the election.
To run for the Senate, Mfume would need to resign from the NAACP because the organization's rules prohibit its officers from seeking or holding public office. He now is free to raise money and campaign.
Competition is expected to be tough for all statewide offices, so an early start would be a boost for Mfume - a man who knows well the road to political office.
Mfume underwent a life-transforming journey from a streetwise youth named Frizzell Gray to a polished politician with a hard-to-pronounce last name.
He grew up in Turners Station, a black enclave in eastern Baltimore County, and later in West Baltimore. By the time he was 16, his stepfather had abandoned him, and his mother had died from cancer. Mfume dropped out of school, picked up odd jobs and fathered five sons by four women before he was 20.
Almost miraculously, he changed his life. He adopted a West African name, using Swahili words for a warrior prince. In 1979, the dashiki-clad young man captured a seat on the Baltimore City Council.
Mfume served two terms on the council before deciding in 1986 to make a bid for the 7th District congressional seat of Rep. Parren J. Mitchell, the renowned civil rights leader who served eight terms in Congress. After defeating a black Republican, St. George I.B. Crosse III, Mfume gained a rising national profile as a leader of the Congressional Black Caucus.
President Bill Clinton needed the votes of the 38-member Black Caucus to get his legislative agenda through Congress, and Mfume often held out for concessions from the president on programs such as the tax credit for the working poor. Mfume, who once had a popular radio talk show on Morgan State University's station, soon became a fixture on nationally televised Sunday TV talk shows.
Still, his tenure on Capitol Hill included stormy moments, particularly when Mfume reached out to the Nation of Islam and its inflammatory chairman, Louis Farrakhan.
After Republicans took control of Congress in 1995, Black Caucus members found themselves outside the spheres of influence. Mfume left for the NAACP.
He remained a presence in local politics - most noticeably five years ago, when many supporters pushed for him to run for mayor of Baltimore. The state legislature approved a change in residency laws, giving Mfume a window for establishing an address in the city and eligibility in the municipal election.
But five months of speculation that stalled the mayoral race ended with Mfume's announcement that he would instead remain with the NAACP. He said then that his "inner voice" told him to remain.
Raymond V. Haysbert, a close friend of Mfume's and former owner of Parks Sausage, said he believes the political and civil rights leader will continue to play a significant role in the state and the nation.
"He's still a young man," Haysbert said.