The selection of Senator Kamala Harris as the Democratic nominee for vice president marks the latest evidence that gender and race have now surpassed geographic balance when it comes to building a ticket for the White House.
Ms. Harris, whose father is Black and whose mother is Indian-American, is not expected to scramble the electoral map, nor was the Biden campaign looking to do so. The former vice president leads in polls of most of the crucial battlegrounds.
Instead, ever since Black voters resurrected his primary candidacy in South Carolina, Mr. Biden and his campaign team have made the pursuit of Black voters in November a centerpiece of his bid for the White House. And he had said from the start of the process that he would choose a woman as his running mate.
Robert Shrum, director of the Center for the Political Future at the University of Southern California, said more than anything the choice of Ms. Harris should address one of the reasons Ms. Clinton lost to Mr. Trump so narrowly in 2016.
“One of the problems in 2016 was a fall-off in the African-American vote in Wisconsin, Michigan and Pennsylvania,” he said.
“She is going to be a great motivator for this ticket,” Representative James Clyburn of South Carolina, a key Biden endorser, said.
“This is 1,000 percent a demographic selection,” said Theodore R. Johnson, a senior fellow at the Brennan Center for Justice, who studies voting behavior among Black voters. He predicted that Ms. Harris would increase Black turnout.
Many Democrats celebrated the history-making choice on Tuesday — no Black woman or woman of color has ever been nominated for vice president or president on a major ticket.
“This has sent a lightning bolt of electricity across a base that has been watching and waiting and looking for a reason to be excited about this race,” said Matt Morrison, the executive director of Working America, a labor-backed political group with three million members. “I have a Black mother who is literally through the roof, and she is emblematic of the visceral excitement of the base that drove Barack Obama to the White House.”