Of course people in the low bracket cheat less, they have absolutely no incentive to cheat. IF they even pay taxes, they're not going to make much by cheating, therefore the punishment of being caught is a lot worse.
If you make more, there is a much bigger incentive to cheat to save even more of your own money. If taxes were lower there would be less of an incentive to cheat. If they get caught, they claim ignorance and just pay back taxes...the same money they've been making interest off of by keeping it.
The only way to slow this is to remove the incentive. Either UP the penalty and investigations, or DOWN the taxes. We know what way McCain wants, lower taxes. We know what way Obama wants, UP the taxes. This creates more of an incentive to cheat, therefore Obama must put more money into investigating fraud.
You pick