trying to understand the math

So I admit math is not my strongest talent. I in fact hate it. I am trying to figure out the math behind the republican economic strategy, which is basically cut taxes and or give tax incentives to the rich and corporations, and tax the hell out of the poor and the middle class.

 so, in a nut shell, we are going to give rich people and corporations more money which supposedly will create jobs( although it doesn't appear to be working that way , it seems the money is going to bonuses) and take more money out of the pockets of the middle class and the poor( leaving them with little to no discretionary income to spend)

I fail to see how this is going to help the economy . with the majority of americans barely making ends meet they will not be buying any products they don't need. this means less money circulating and if no one is purchasing goods and services then companies are going to either close or downsize. less jobs-less money - horrible downward spiral.

makes no sense.