The gap in presidential vote preference between white and nonwhite voters has shrunk by a surprising 16 percentage points since 2016, according to an Upshot analysis of pre-election polls, as Joe Biden gains among white voters and President Trump makes inroads among Black and Hispanic voters…

Over all, Mr. Trump leads among white voters by only five points in high-quality surveys conducted since the Republican National Convention in August, compared with a 13-point advantage in the final surveys before the 2016 election. Not only does Mr. Trump fall short of his own lead with that group from 2016, but he also underperforms every recent Republican presidential candidate since Bob Dole in 1996…

In recent national polls, Mr. Biden leads by 42 points among nonwhite voters, 66 percent to 24 percent. It’s about nine points worse than Mrs. Clinton’s 51-point lead in the final 2016 surveys.

Mr. Biden has lost almost exactly as much ground among nonwhite voters as he has gained among white voters, but trading nonwhite for white voters is a favorable deal for Mr. Biden. White voters outnumber nonwhite voters by more than two to one, and by an even greater ratio in the most important battleground states.