Philip Wallach: “If we look at all 401 contests in which a single Democrat faced a single Republican, there is not much difference. Relative to baseline expectations derived from their districts’ recent voting patterns (as calculated by the Cook Partisan Voting Index), 144 Trump-endorsed candidates exceeded their baselines by an average of 1.52 points. In 257 races where Trump did not endorse a general-election candidate, Republicans exceeded their baseline by 1.46 points.”
“But that similarity is driven mainly by Trump’s endorsements of many Republicans cruising to easy reelection in uncompetitive districts. If we focus exclusively on districts where the margin of victory was less than 15 points, such that the seat was conceivably in the balance, the picture that emerges is quite different.”
“In these 114 districts, candidates bearing Trump endorsements underperformed their baseline by a whopping five points, while Republicans who were without Trump’s blessing overperformed their baseline by 2.2 points — a remarkable difference of more than seven points.”
