It’s been a real “well, shit” few days for Democrats, for which one could either blame the New York Times or the underlying reality on which the New York Times reports. On Monday, the Times’ Upshot section released a new poll in which Republicans led Democrats by just over three points when respondents were asked which party’s candidate they supported in their district—a gain of about four points for the GOP in the last month on the measure. It was the latest such “generic ballot” question on which Republicans have made gains over that time, and the party has closed...