The most conservative class is normally the petite bourgeoisie. Not the top, not the bottom, but one up from the bottom. The lower-middles are especially opposed to benefits for the bottom class - even if it means giving massive breaks to the rich.
The Economist cites new research on this puzzle. It is not that Joe the Plumber('s assistant) really expects to be in the top tax bracket someday that makes him oppose raising taxes on the rich. It is because he doesn't want there to be any money redistributed to the class below him, which might raise them up to his level.
"Last-place aversion," more than rich envy, makes the petite bourgeoisie so passionately opposed to welfare.