The Disappearing Political Center: In More Places, Elections Aren’t Close

For a stark illustration of how the political center is disappearing from American politics, compare President Bill Clinton’s re-election in 1996 with Donald Trump’s victory 20 years later.

In 1996, Mr. Clinton won re-election easily, and yet the outcome was relatively narrow in many parts of the country. In 1,125 counties, Mr. Clinton won or lost by a margin of less than 10 percentage points.

In 2016, by contrast, Mr. Trump won or lost by a single-digit margin in only 310 counties—even though the national popular vote was much closer...