The rallies are not resulting in huge numbers of votes, that much is not debatable. Now some people here will tell you its just massive, coordinated fraud. Is it? Maybe, maybe not. The problem I have is that they can never cite any actual proof, just a bunch of massaged numbers and opinions do not make conclusive proof. Its also realllllly hard to coordinate something like that on a massive scale and have no smoking guns. I think the more likely explanation is that these events have sizeable contingents of people who cannot vote; either they're from out of state, not registered, not registered Republican (if a closed primary), whatever the case may be. So everybody sees 4,000 people and think its going to equal 4,000 votes, and when it doesn't, they cry foul.
I think more, smaller venues would pay higher dividends. Its certainly worked for Santorum.