It's His Judgment, Stupid
Even if you take him at his word and give him every benefit of a doubt, even if you cut him some slack for being more willing than most politicians to admit mistakes, even if you dismiss as tawdry the insinuation of an affair that the Times couldn't prove, the article makes it quite clear there's something seriously wrong with McCain's judgment. The deal breaker - what makes him utterly unqualified to be president, especially now - is that he seems incapable of improving it. He makes the same mistake over and over again. Here's an overlooked nuance from the second paragraph:
A female lobbyist had been turning up with him at fund-raisers, visiting his offices and accompanying him on a client’s corporate jet. Convinced the relationship had become romantic, some of his top advisers intervened to protect the candidate from himself — instructing staff members to block the woman’s access, privately warning her away and repeatedly confronting him, several people involved in the campaign said on the condition of anonymity.Aides - plural - repeatedly had to confront McCain about his inappropriate relationship with a lobbyist. Once or twice wasn't enough for him to get the message. This is a persistent theme in McCain's behavior.
In fact, the Iseman incident itself was a reprise of similar behavior. Ten years earlier, to use the Times' word, McCain had done an "official favor for a friend with regulatory problems" and found himself knee deep in the Keating savings and loan scandal, barely escaping with his career. And then, with Iseman, "Mr. McCain had written letters to government regulators on behalf of" his new friend's client.
But there's more. Not only had McCain gotten in trouble for the earlier favor-mongering, he even realized, albeit belatedly, what his mistakes were - being too trustful of daring, confident, people; getting too close to people with business before the government, and so on. Even understanding this, he acted the same way with Iseman (regardless of whether you believe his denials of an affair).
In other words, McCain admits his judgment is frequently awful. Even when he knows better, he can't help himself sometimes- he's easily, and dangerously, swayed by strong personalities and by his need for friendships with such people. But think about what that means. Even if you cut him slack on a personal level - something along the level of, "well, at least he has the courage to admit he's wrong and the insight to know why" - this is not the kind of personality you want negotiating with Vladimir Putin, to pick just one example.
Sure. Everyone makes mistakes. And even though McCain makes spectacular mistakes, that in and of itself isn't the real crux of the problem. Rather it's this: By his own admission, McCain can't learn from his mistakes. He knows himself that his personality is too rigid. That is the critical difference between John McCain and a truly qualified candidate for President of the United States. And no amount of straight-shooting hype will change that.