The theory of the Overton Window -- named after political theorist Joseph P. Overton -- describes the snapshot of what's acceptable to voters:
The Overton window is a political theory that describes as a narrow "window" the range of ideas that the public will respond to as acceptable, and that the political viablility of an idea is primarily defined by this rather than individual preferences of a given politician....At any given moment, the “window” includes a range of policies considered to be politically acceptable in the current climate of public opinion, which a politician can recommend without being considered too “extreme” or outside the mainstream to gain or keep public office.
It's axiomatic among "smart" political observers that the Paul Ryan budget is outside the Overton Window.
They maybe right. But they also may be forgetting that there are really only two ways to campaign for the White House. You can either pander -- tell voters roughly what they want to hear, confirming their basic views -- or you can persuade.
It's been a long time since an American politician tried the latter approach. Paul Ryan -- and Mitt Romney -- may discover that the window is open a lot wider than they thought.