While there is some disagreement in the profession of political science about how polarized the American electorate is, there is undeniably considerable polarization in the U.S. Congress. The post-World War II period of bipartisanship on both on foreign affairs and the conservative coalition (Northern Democrats and Southern Democrats) on domestic legislation, was replaced beginning in the late 1970s and accelerating in the 1980s by high levels of polarized voting. Legislative polarization is typically measured by roll call voting patterns, showing greater inter-party differences, and the data clearly show rises in polarized voting beginning in the late 1970s.