That North Carolina result would hardly be a surprise, of course: It has been a razor’s-edge state for three straight elections. President Obama won it in 2008 by 0.4 of a percentage point over John McCain, then lost it by two points to Mr. Romney four years later. Mrs. Clinton leads there by a mere 1.4 points in the Real Clear Politics polling average. The Upshot forecasting model gives her a relatively narrow edge of 63-37, and the FiveThirtyEight model has it even closer, with a 53 percent chance for a Clinton victory.

In polarized America, it seems, there are red states and blue states, and nothing much else matters. How locked in has the electoral map been over the last decade? If The Upshot model predictions prove correct, with Mrs. Clinton winning North Carolina, the 2016 map will look exactly like the 2008 map — except that Republicans would win Indiana.