The facts are all on the Republicans' side. But, unless someone articulates those facts, they will be like the proverbial tree that falls in an empty forest.
What are called "tax cuts for the rich" have been reductions in high tax rates under four different administrations, including the Democratic administration of John F. Kennedy. In each case, going all the way back to the 1920s, the reduced tax rates have led to increased tax revenues for the government.
"The rich" have ended up paying both a higher total amount of taxes and a larger share of all taxes than they did before what were called "tax cuts for the rich." The reason is very straightforward: high tax rates that people don't actually pay do not bring the government as much revenue as lower tax rates that they do pay.
High tax rates drive investors into tax shelters like tax-exempt bonds or drive their investments out of the country altogether, costing Americans jobs. This is not rocket science-- and the data are there to prove it. But somebody has to say it.
Unlike Rocky Marciano, Republicans don't seem to see a need to work on their punches. They are going to need some knockout punches if Barack Obama calls their bluff on raising the national debt limit, and there is a government shutdown that will be blamed on the Republicans. A few light jabs will not save them.