For a half century, Democratic presidential prospects have depended on the nominee’s receiving an overwhelming percentage of a robust black turnout (blacks are 8 percent to 13 percent less likely than whites to turn out). Over the last ten presidential elections, the Democratic candidate has averaged only 39 percent of the white vote but 88.9 percent of the black vote. These are the black-vote percentages:

USA Today currently has Kamala Harris winning 72 percent of the black vote and Donald Trump 17 percent. It’s unclear whether Barack Obama’s recent tin-eared pitch to black males will move the needle appreciably. Unless Harris significantly increases her percentage of the black vote during the next two weeks, her electoral prospects are bleak.