I always thought the "trickle-down theory" — cut taxes for the very rich and all sorts of benefits will trickle down to the poor and middle-class — was a scam. Some rich guys paid a good con-artist to come up with some way they could argue that they should pay a lower percent of their income than my cleaning lady pays of hers. And I've always doubted that most of the people pushing the idea even believed it. George H.W. Bush famously called it "voodoo economics"…but Ronald Reagan and the G.O.P. wanted it and he wanted to be Reagan's vice-president so he changed his mind and supported it. It has never worked the way it's supposed to but when you point that out to the folks who advocate it, they usually come back with "Oh, it will, it will. We just have to try more of it."
That theory has performed so badly that a lot of its former champions no longer even want to sell or defend it. They've come up with a new mantra that they hope will get them to the same place: "You know, the rich are job-makers so if we cut their taxes, they'll be able to afford to create more jobs." Of course, if they really believed that, they wouldn't cut taxes for the rich. They'd give them some sort of deduction incentive — i.e., you'll pay less in taxes if you create more jobs. But that's not the goal here. The goal is to convince the poor and middle-class that they'll be better off if rich people didn't pay so much. Amazingly, a lot of people buy that.
Anyway, here's one my favorite political writers, Gene Lyons, to give you his take on this whole matter.