Tucker Carlson's explanation was probably more accurate:
McCain ran an entire presidential campaign aimed primarily at journalists. He understood that the first contest in a presidential race is always the media primary. He campaigned hard to win it. To a greater degree than any candidate in thirty years, McCain offered reporters the three things they want most: total access all the time, an endless stream of amusing quotes, and vast quantities of free booze.
I saw reporters call McCain "John," sometimes even to his face and in public. I heard otherse, usually at night in the hotel bar, slip into the habit of referring to the Mccain campaign as "we"- as in, "I hope we kill Bush." It was wrong, but it was hard to resist.