The unscripted comment by Obama that “you didn’t build that” turns out to have a background. Not to mention a long history, dating back to Teddy Roosevelt. (Yes, way, way back) But it has been a consistent theme of the “progressives” and Communists (no real distinction) ever since.
Heritage had a nice article on it today, which you can read here.
It is now fairly sweet that the Republicans have chosen a theme of “we did build this” for the convention.