That Mark Penn would one day step aside from the Clinton campaign has been, as they say in sociology, overdetermined for a while. He had few allies inside the campaign, he was subject to withering criticism in the press, and he simply refused to give up his outside work, some of which conflicted with Sen. Clinton's policy positions.

After Thursday's disclosure in the Wall Street Journal that Penn had met with the Colombian government about its trade agreement, Clinton's aides were put in the position of not being able to come up with a defense for Penn; he had done the indefensible. For Clinton, who has tolerated Penn's public errors in judgment because she believed in his strategy, it was the last straw.

"The senator and president were very angry about the meeting. Mark knew that he had made a very big mistake and decided to step aside," a senior campaign official said tonight.

Penn will continue to serve as the campaign's chief pollster. But it unlikely he will serve the campaign in any public capacity, such as participating on press conference calls or appearing as a television surrogate.

Geoff Garin, who began polling for the campaign last month, and Howard Wolfson, the campaign's communications director, will take over messaging and strategy duties.

Here is the statement from campaign manager Maggie Williams:

After the events of the last few days, Mark Penn has asked to give up his role as Chief Strategist of the Clinton Campaign; Mark, and Penn, Schoen and Berland Associates, Inc. will continue to provide polling and advice to the campaign.

Geoff Garin and Howard Wolfson will coordinate the campaign's strategic message team going forward.