Mr. Biden’s campaign said it was beginning to build a team to conduct a “vigorous vetting process.” Some close to the campaign say the team is in the early stages of compiling a list of potential running mates and then will vet them. Beyond his own experience as Barack Obama’s vice president, Mr. Biden has a deep bench of aides to consult. One of his closest advisers, Ron Klain, helped do vice-presidential vetting for Al Gore in 2000.

Mitt Romney cut his campaign’s list of about 80 potential running mates to 20 in early April 2012. By late July, the list had been narrowed to five men, after the one woman under serious consideration, former Secretary of State Condoleezza Rice, declined the campaign’s invitation to be vetted. (Mr. Romney eventually chose Representative Paul Ryan.)

Donald Trump’s 2016 vetting process was less streamlined, but among those he interviewed during his search was Senator Joni Ernst of Iowa.

Mrs. Clinton started with a list of 40 possible candidates, which was narrowed to nine who underwent a process of serious vetting, an interview and a campaign appearance with the candidate. While she considered a number of women to be vice president, only Ms. Warren advanced to the final stages of the process.

For Mr. Biden, 77, a much younger woman could assuage concerns about his age and critiques about a primary process that started with the most diverse field in history and ended with two white men.

Mr. Biden’s campaign hopes the early announcement that he would select a woman will give his operation a shot of enthusiasm from voters, even as the presidential election heads into a deep freeze because of the coronavirus. On Thursday, his campaign sent a fund-raising appeal asking supporters to “commit to standing with” Mr. Biden and his future female running mate.

By announcing he will pick a woman, Mr. Biden is aiming to give his ticket a modern-day balance in a party focused on issues of racial and gender representation. Past nominees have chosen running mates who provided geographic diversity (Lloyd Bentsen in 1988) or offered the promise of winning a key state (Mr. Ryan, from Wisconsin, in 2012). Mr. Obama, just four years into his Senate term, chose Mr. Biden in 2008 to ease concerns about his own relative lack of experience and help appeal to white working-class voters.