How Kamala Harris decided on her running mate, Tim Walz

Vice President Kamala Harris spent this past weekend interviewing the top contenders on her VP shortlist, meeting in person at her Washington, D.C. home with Govs. Tim Walz and Josh Shapiro, and Arizona Sen. Mark Kelly.

It was just 16 days ago that President Joe Biden dropped out of the race, and Harris and her vetting team, led by former Attorney General Eric Holder, were operating in a truncated time frame. The vetting team initially cast a wide net, with more than a dozen people in consideration. That list quickly got shorter, with nine people being formally asked to submit vetting materials.

It's a process that is extensive and one that would typically take months – but Holder, along with his vetting team led by former White House counsel Dana Remus, campaign chair Jen O'Malley Dillon, campaign chief of staff Sheila Nix, and Harris's brother-in-law Tony West – wrapped up their work on Friday, turning it over to Harris for a final decision.

Harris met with her vetting team on Saturday and was provided with extensive briefings on each candidate under consideration. She would then interview her top choices.

Following Harris's interview with Pennsylvania Governor Josh Shapiro, there was a sense among Shapiro's team that the meeting did not go as well as it could have, sources familiar with the matter tell ABC News. Later Sunday, after the interview, Shapiro placed a phone call to Harris' team, indicating he had reservations about leaving his job as governor, sources said.

Walz, on the other hand, had an indication Monday evening that he would be chosen as Harris' running mate, sources familiar with the matter said.

Harris came to her decision on Monday and told a small group of staff, sources said. She did not place a phone call to Walz until Tuesday morning.