It was a gentle but unmistakable nudge President Obama gave Representative Charles B. Rangel recently, suggesting in an interview three weeks ago that Mr. Rangel, 80, should retire to “end his career with dignity.”
At a tense and sometimes fiery candidates’ forum Monday night, Mr. Rangel shot back that it was not his dignity the president should be worried about.
“Frankly, he has not been around long enough to determine what my dignity is,” Mr. Rangel said of the 49-year-old Mr. Obama. “For the next two years, I will be more likely to protect his dignity.”
The unexpected eruption seemed to reflect the increasingly bitter relations between the embattled 20-term Democrat from Harlem and a president who is trying to protect his party’s prospects in a difficult midterm election season.
And it came during an uncomfortable evening for Mr. Rangel, who made a rare appearance with his five challengers and found himself facing harsh public attacks in front of his constituents at a Baptist church in the heart of his Harlem district.
Long accustomed to being showered with praise and accolades, and surrounded by friendly crowds who treated him like a folk hero, Mr. Rangel could not escape the controversy that has shaped his re-election bid: the 13 charges of ethical violations issued against him by a House panel last month, including hoarding below-market apartments and improper fund-raising.
The best known of his Democratic challengers, Adam Clayton Powell IV, accused Mr. Rangel of “years and years of corruption.”
“Four rent-controlled apartments. Four!” he yelled.
“It’s a slap in the face to his community!” Mr. Powell thundered.
Mr. Rangel, sitting a few feet away, fidgeted in his chair and fingered some papers, his eyes occasionally darting around the room.
But Mr. Powell did not let up, likening Mr. Rangel’s ethics troubles to a rotting tree: “To have good fruit, you must have a healthy tree. We no longer have a healthy tree, and we will no longer have good fruit.”
The candidates spoke in the sanctuary of the Convent Avenue Baptist Church in western Harlem. Organizers, including some tenants from Mr. Rangel’s apartment complex, appeared determined to tilt the evening in Mr. Rangel’s favor.
They announced unusual rules, just minutes before the forum began, barring photography and videotaping of the forum, ensuring that any heated moments or slip-ups by Mr. Rangel would not turn up later in a rival’s political ads.
The format for the forum, laid out days ago, had originally called for all the candidates to stand on stage at once, putting them on equal footing. But at the last minute, the organizers e-mailed each campaign with a “slight change”: Mr. Rangel would appear on his own, instead of sharing the podium with his challengers.
His rivals cried foul — Mr. Powell called it “the Democratic machine playing tricks” — but they relented.
The crowd that gathered was pro-Rangel, too. At one point, Jonathan Tasini, a candidate and a labor activist, explained matter-of-factly that Mr. Rangel had accepted large sums of money from political action committees. The crowd erupted in boos and jeers. A woman in a straw hat stood up and wagged her finger at Mr. Tasini.
But Mr. Rangel’s problems kept intruding.
Mr. Tasini told the crowd that, despite Mr. Rangel’s best intentions, he had fallen victim to a culture in Washington that was awash with corporate money and lobbyists.
“The corruption that Congressman Rangel is a part of is being in Congress for 40 years,” Mr. Tasini said.
Mr. Rangel’s foes took pains to honor his 40-year career in Congress. But they made clear they thought it was time for a change. “Yes, he has done some good. He has a legacy,” Mr. Powell said.
“But he is no longer the chairman of the powerful Ways and Means Committee. He is no longer perceived as somebody that people in Congress want to work with.”
Mr. Rangel infused his own remarks with his typical sarcasm and combativeness, taking a jab at those who had called on him to step aside, especially Mr. Powell.
“Adam, is he here?” Mr. Rangel said, quickly surveying the room. “He truly believes that I should resign, so that somebody else should take my place.”
The crowd interrupted: “No!”
“He is the only one to say this,” Mr. Rangel continued. “I think it’s creative.
“But if it’s O.K. with my doctor, I am going to serve the next two years.”
Mr. Rangel also railed against the wars in Afghanistan and Iraq, saying American soldiers would not be there if not for the country’s voracious appetite for oil, and mocked Republicans in Congress for trying to block the president’s agenda.
And while some Democrats have said that he is creating an embarrassment for his party by refusing to step down, Mr. Rangel declared, “I won’t step aside when the people of my district believe this is what I should be doing.”
While Mr. Powell, whose father once held the seat, was aggressive, the other candidates challenging Mr. Rangel were more subtle, though they echoed his essential message: Mr. Rangel’s era was over.
“Everyone has their time,” said Joyce S. Johnson, a former field director in New York for Mr. Obama’s presidential campaign in 2008. “There is a need for a new perspective, out-of-the-box thinking.”
The other participants were Vince Morgan, a banker, and Craig Schley, a community activist; all are running as Democrats, except for Mr. Schley, who is campaigning as an independent.
In a brief interview after the forum, Mr. Rangel elaborated on his remarks about Mr. Obama, making clear he did not believe anyone so junior to him had any place weighing in on his long career and stature.
“My dignity is 80 years old,” he said. “How can somebody so much younger tell me how to leave with dignity?”
Asked how it felt to be publicly attacked in his district by his rivals, he laughed, smiled and said, “It’s all part of the campaign.”
After the last candidate spoke, the crowd swarmed around the pinstripe-suited Mr. Rangel, who marched up the aisle, reaching out to shake hands, and offer kisses to women gathered in the pews.
He stopped briefly at the doors of the church to greet former Mayor David N. Dinkins, who has been an especially visible defender of Mr. Rangel, giving a middle finger to a protester at Mr. Rangel’s birthday party this month.
Thinking about running for eighth grade class president at Nettleton 
