At the moment, a reasonable estimate is that Mr. Biden is performing four or five points worse among likely voters in the critical states than he is among registered voters nationwide. As a result, he holds only a narrow and tenuous edge in the race for the Electoral College, if he holds one at all…

The president begins the campaign with strong support from the white working class who powered his upset win four years ago. He leads among white voters without a college degree, 61 percent to 32 percent, in an average of live-interview polls conducted since March 15, matching or perhaps even exceeding his margin over Hillary Clinton in methodologically similar polls conducted late in the 2016 campaign.

The results suggest that Mr. Biden, despite his reputed appeal to blue-collar workers, has made little to no progress in winning back the white voters without a college degree who supported Barack Obama in 2012 but swung to Mr. Trump in 2016.