He got testy today on his campaign plane with a NY Times reporter.
I suppose most people will immediately see this as rebounding negatively for McCain.
And yes, it could--it could reinforce the idea out there that he's a loose cannon, that his temperament is unpresidential, etc.
On the other hand, conservatives don't like the NY Times. This kind of thing will simply bring some of them closer to him (and don't think McCain doesn't know that). And I don't think very many people in America are too sympathetic to the Times. It's seen as a representative of elite thinking unsympathetic to the average American. I suspect there are few average Americans out there too sympathetic to it. Don't think that McCain doesn't know that, either. He may have known, when he began the testy exchange with the Times' reporter, that something like this could help him.
Still, I reiterate: I just don't think John McCain will be able to rally the conservative base back to him, and I don't think he's in a good position to win in the fall. This is a "change" election; Senator McCain's age and his long tenure in Washington un-suit him for winning this time.