Empirical models of spatial voting allow legislators' locations in an abstract policy or ideological space to be inferred from their roll call votes. Over the past 25 years, these models have provided new insights about the US Congress and legislative behavior more generally (see, for example,...

The idea of America as politically polarized—that there is an unbridgeable divide between right and left, red and blue states—has become a cliché. What commentators miss, however, is that increasing polarization in recent decades has been closely accompanied by fundamental social and...