Tood Purdum's Vanity Fair profile of Bill Clinton has all sorts of good stuff, but this anecdote is particularly enjoyable:
Less amusingly, in the run-up to the 1996 re-election campaign, when Clinton took one of his many fund-raising trips to California, I teasingly asked his press secretary, Mike McCurry, whether the president intended to go jogging with Eleanor Mondale, the daughter of the former vice president—as he had on a previous trip—after he was spotted with her (and Barbra Streisand) in the wee hours of the morning. The next day, as we boarded the plane at Andrews Air Force Base en route to Los Angeles, McCurry, whose effectiveness as Clinton’s spokesman was aided by the fact that he never fell in love with him, sidled up to me and told me that he had passed my question on to the president, and that Clinton had responded, in vivid terms he knew I could not print, that I should not confuse exercise with extracurricular activity.
Only much later would the world learn that no less an informed observer than Monica Lewinsky, whose judgment, in hindsight, has often seemed sounder than the president’s, had taken note of Mondale’s presence at his side. According to Andrew Morton’s authorized account Monica’s Story, Lewinsky flew into a swivet when she was once stopped at the White House gate on her way to a hoped-for meeting to deliver Christmas gifts to the president. While waiting, she learned that Mondale was with him in the White House.
“Do you think I would be stupid enough to go running with someone I was foolin’ with?,” Clinton later asked Lewinsky. Without missing a beat, she replied, “Do you want me to answer that?”
See Ross Douthat for speculation on why a piece like this one, which has a LOT of information on Bill's extracurricular activities, is only now being published.