In Washington, Americans have two-party government, with a Democratic president and Senate and a Republican House. We had it before November's election and will have it again for the next two years.
Looking back from 2014, we will have had two-party government for most of the preceding two decades, for six years of Bill Clinton's presidency, three and a half years of George W. Bush's and four years of Barack Obama's.
But in most of the 50 states, American voters seem to have opted for something very much like one-party government.
Starting next month, Americans in 25...