Remarkably, Mr. Trump’s lead among white voters has all but vanished. On average, he holds just a three-point lead among white voters, 48 percent to 45 percent, across an average of high-quality telephone surveys since June 1. His lead among white voters has steadily diminished since April…

Over the last two decades, Republican strength among white voters has given the party structural advantages in the House, the Senate and the Electoral College. A competitive race among white voters would deprive Republicans of those advantages, threatening carefully devised gerrymanders and raising the specter of previously unimagined losses in the Senate…

Republicans in the House may also face severe consequences. In this analysis, Mr. Biden would carry a staggering 260 congressional districts, including a half-dozen in Texas. He could even carry districts where Mr. Trump won by double digits in 2016, like Missouri’s Second, Indiana’s Fifth, Arizona’s Sixth, Florida’s 16th, or Ohio’s 12th and 14th. Mr. Trump would win another set of 25 districts by less than five points each. Many of these districts were only somewhat competitive in the 2018 midterms, while many others were not competitive at all. Already, various ratings outfits like the Cook Political Report have classified them as competitive.