Bloomberg reports that McCain's campaign has been lying about the(!) size of his crowds. To be more accurate, the sources of the crowd estimates.
It's one thing to exaggerate the size of crowds, but to tell a discernible lie about the source of the estimate is arrogant, stupid or both.
The fact is that no one has ever developed a good method for accurately computing the size of crowds in open areas. (Events like Obama's in Denver are different, because the number of seats in the stadium gives at least a basis for a reasonable estimate.) Year ago, I read--maybe from the great Teddy White--that part of the job of an advance man was to stand next to the police chief where he could say, "Pretty good crowd, chief. What d'you think, 8,000 people?" "No, not that many." "Maybe 6,000?" "Could be." And then the chief would tell the press that 6,000 people were in a crowd that might have been 4,000.