This chart from Dan Rodrik (via Kevin Drum) shows income growth during the tenures of Democrats and Republicans. With Democrats, the poor do better than the rich (percentage-wise). With Republicans, the rich do much better than the poor. But they still don't do as well as they do under Democrats.
Bartels shows in his book that this difference is not a statistical artifact or a fluke. It is not the result of Democrats coming to power during better economic times, or of Republicans reining in the unsustainable excesses of Democratic administrations they replace. (It turns out that the same pattern prevails even when a Republican president is succeeded by another Republican.) These numbers are real and they are the outcome of partisan differences in policy. So if you are one of those who have bought the story that income distribution is the result of pure market forces and technological changes, with politics playing no role--think again.
How the Republicans have come to be thought of as the party of growth is a question beyond my capacities.