The problem with crowd size is that it doesn’t necessarily mean the crowds that turned out for Obama 4 years ago are not voting for him or are less excited. Their new messiah is known to them now.
It is the same thing with signs and stickers. He was new and when something is new we celebrate.
A new marriage,a new baby, a new house, are all times we celebrate. After the marriage is 4 years old, or the baby is 4 etc, doesn’t mean we are love our spouse, child or home less.
I follow your logic about the new wearing off. However think back to that crowd in Ohio this exact weekend in 2008 where he had 80,000 and this year 4,000. I would assume at least 75% of that 80,000 would have voted for him on the low end which would be around 60,000. Now let’s assume that 100% of those 4,000 will vote for him as they are still the ones with enough enthusiasm to get out there. Let’s also assume those are not bussed in paid fans but true Obama voters. That is still a 56,000 vote difference. That is more than just the new wearing off I think. I think that will play a significant role in Romney’s win on Tuesday.