A person within the Clinton campaign said Sunday that Mrs. Clinton was “disappointed” that Mr. Penn had taken on Colombia as a client and had met with Colombian officials to advise them on how to win passage of a pact she has publicly denounced.

Mrs. Clinton was said to be furious when she learned that he was employed by and consulting with the Colombians on the trade treaty.

Mr. Penn apologized Friday and said the meeting had been a mistake. The Colombians, offended by what they called an insult from a hired lobbyist and spokesman, fired him and Burson-Marsteller on Saturday.

The Clinton campaign aide said Mr. Penn concluded over the weekend that he had to step aside as chief strategist to avoid further embarrassment to Mrs. Clinton. She did not try to talk him out of it, but the aide said Mrs. Clinton did not dismiss him outright. “He will continue to provide polling and advice as part of the team,” the Clinton aide said.

Mr. Penn is deeply unpopular among Mrs. Clinton’s most loyal aides because of his reputation as a self-promoter, his refusal to accept responsibility for the campaign’s setbacks and because he has refused to sever his ties to Burson-Marsteller.

He has engaged in a number of widely reported conflicts with other top aides, particularly Mandy Grunwald, a longtime and extremely loyal advertising expert who has advised both Clintons since Mr. Clinton’s 1992 presidential campaign.

Mr. Penn has also disavowed any responsibility for the campaign’s blunders and its poor performance in the Feb. 5 Super Tuesday contests, in which Mrs. Clinton lost the presumed inevitability of her nomination. In an interview with The Los Angeles Times, he said he had nothing to do with the campaign’s day-to-day message and was chiefly a pollster. That infuriated other aides who welcomed his demotion on Sunday, according to campaign officials.

Among Mr. Penn’s other public relations clients was Countrywide Financial, the nation’s largest home mortgage lender, which operates in an industry that Mrs. Clinton has criticized. Burson-Marsteller has also provided public relations advice to Blackwater Worldwide, the private security firm under investigation by numerous government agencies for the deaths of civilians in Iraq.