The old saying "never pick a fight with a man who buys ink by the barrel," still holds. Press coverage of John McCain has become steadily more unfavorable since a senior adviser attacked the New York Times.
Now, attributing the negative coverage to McCain's attacks on the press is a bit simplistic. In the same period, McCain's poll numbers have dropped, he has attacked Obama, and the economic news has been uniformly bad, all of which might lead to negative coverage. Still, attacking the press for reporting unflattering facts (i.e. doing its job) is unlikely to improve your coverage.