Dani Rodrick posts this chart from Larry Bartels' forthcoming book. It shows that under Republican administrations, incomes grow strongly for rich people, but barely at all for those of more modest means. Under Democratic presidents, by contrast, lower income groups see stronger income growth but everyone's income grows faster than it does under the GOP.
That's striking stuff. Indeed, it's almost too striking. The president's control over domestic policy is pretty circumscribed and public policy has only a limited influence over the economy, so it's surprising to see such a strong effect. I'll be interested to read the book and see Bartels' account in more detail.