According to the Pew study, 76 percent of poor Republicans believe most people can get ahead with hard work. Only 14 percent of poor Democrats believe that. Poor Republicans haven't made it yet, but they embrace what they take to be the Republican economic vision - that it is in their power to do so. Poor Democrats are more likely to believe they are in the grip of forces beyond their control.
The G.O.P. succeeds because it is seen as the party of optimistic individualism.
Or, you know, the party of cognitive dissonance and misdirected class envy.