Time: It is impossible to overstate how fundamental a change Penn's exit represents in Clinton's campaign

Mark Halperin writes in Time:

Penn has been a controversial figure throughout the campaign, alienating colleagues with his brusque manner and pursuing a strategy emphasizing Clinton's toughness, experience, and electability, at a time when most analysts in both parties see an electorate demanding change.

Although the campaign's statement announcing Penn's departure as chief strategist suggested he would continue to give advice to her effort, it is impossible to overstate how fundamental a change this represents in Clinton's campaign. Penn has had almost full autonomy to make major decisions involving what the candidate says, where she goes, and what gets conveyed in her advertisements. Even as many in the campaign had turned sour on Penn, he reportedly enjoyed the confidence of both Hillary and Bill Clinton.