Geographic balance takes a back seat to gender and race.

Gender and race have now surpassed geographic balance when it comes to building a ticket for the White House.

By selecting Ms. Harris, a Californian who represents a state that Democrats have captured in every presidential election since 1992, Mr. Biden embraced the modern imperatives of Democratic coalition building that have made the days of choosing running mates because they could deliver their home states a relic.

Ms. Harris, who is half Black and half 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 chose a woman as his running mate.

“She is going to be a great motivator for this ticket,” declared Representative James Clyburn of South Carolina, a key Biden endorser.

If Ms. Harris does not put any particular new state into play, Democratic strategists and Biden allies were hoping her spot on the ticket could increase turnout and Mr. Biden’s margins across the map and strengthen his position in states that Hillary Clinton lost in 2016, in no small part because of a drop in voting by African-Americans.