Voters don’t choose divided government. It’s chosen for them by a system, unique in the democratic world, of multiple overlapping elections held at different intervals in which different electorates fill different offices, none of whose occupants have ultimate responsibility. The electorate of 2008 chose Obama and the Democrats. The electorate of 2010—consisting mainly of McCain voters, and smaller by forty-five million—chose the Republicans. Hardly anybody voted as they did out of a desire for “divided government,” as opposed to a desire for a government that would embody their own political and ideological leanings.
Hendrik Hertzberg, from a brief blog post.