Historically, whenever the Democrats are running the government, the economy does better and everyone gets richer. When the Republicans are in charge, the rich do slightly worse off than if Democrats were in charge, but they do way better than everyone else who suffers in squalor until Republicans are voted out of office.
Here’s a chart mapping this phenomenon with data provided by Princeton Politics and Public Affairs Professor Larry M. Bartels. This data shows what happens when a Democrat is in the White House versus a Republican.
And here’s a Rachel Maddow episode further expanding on this idea that Democrats can’t seem to convey on their own.