By Dan Merica, Jeff Zeleny and MJ Lee, CNN

(CNN) -- Joe Biden started with Kamala Harris, and in the end, came back to her.

Biden interviewed the California senator over video chat as he entered the homestretch of his search. And although the former vice president would ultimately interview 11 prospective running mates in the span of 10 days, Biden ultimately went with the woman who had always made the most sense to him.

CNN spoke to more than a dozen Biden advisers, friends and top Democrats involved in the campaign's search who painted a picture of a deliberative and intense process, one that saw the former vice president actively consider a range of candidates even as many around him believed the position was Harris' to lose from the outset.

The search was complicated by the coronavirus pandemic, with Biden unable to spend considerable time on the campaign trail with any of his prospective running mates. Candidates like Michigan Gov. Gretchen Whitmer and others rose to greater prominence over the last several months of protests and pandemic, but Harris always had a key edge: Biden has a familiarity with the California senator that grew during their time in the Democratic primary.

When Biden finally met with Harris virtually, he already felt a "genuine personal connection," a source said.

Some close to the former vice president harbored negative feelings about the way Harris pointedly attacked Biden on issues of race during the first Democratic debate in 2019. Those concerns raised such alarm bells among high-profile Harris supporters that they organized a call with the campaign to defend the California senator.

But multiple people who Biden spoke with during the vetting process said they got a sense that Harris was always a top choice.

"I always felt he would come back to his comfort zone," said a close Biden friend, "which was Kamala Harris."

Biden long believed that Harris was arguably the strongest choice for the job, the sources said, with the former vice president drawn to the fact that the California senator knew the rigors of a national campaign after running for president herself, was widely popular inside the party and fulfilled his primary desire of picking the person who would make the best governing partner.

"If we're going to get through these crises, we need to come together and unite for a better America," Biden wrote his supporters on Tuesday, explaining his decision. "Kamala gets that."

The interview with Biden was the final phase of the candidate's extensive vetting process, one that began with prospective candidates submitting documents to a search committee led by former Connecticut Sen. Chris Dodd, Delaware Rep. Lisa Blunt Rochester, Los Angeles Mayor Eric Garcetti and Biden adviser Cynthia Hogan.

Harris, one source said, spoke at length about her close relationship with Beau Biden, the former vice president's late son, in her interview with Biden's search committee.

In all, 20 candidates first met with the search committee, which conducted interviews in pairs with the prospective running mates. Questions ranged from policy and agenda queries to more off the wall questions, like what each contender thought President Donald Trump's nickname would be for them.

The committee then prepared presentations on each prospective candidate for Biden and his wife, Jill, to review as they worked to whittle the field to a manageable number of one-on-one interviews. Biden also met with each co-chair one-on-one to solicit their running mate suggestions.

Biden informed Harris she was the pick via video chat 90 minutes before the campaign announced the decision, but the former vice president spent much of the day calling other prospective running mates -- including Whitmer, Illinois Sen. Tammy Duckworth, Massachusetts Sen. Elizabeth Warren, Georgia Democrat Stacey Abrams, Atlanta Mayor Keisha Lance Bottoms and California Rep. Karen Bass -- to inform them that they were not his choice.

"You ready to go to work," Biden asked Harris, according to a video of the moment provided by the campaign.

"Oh my god," Harris said. "I am so ready to go to work"

Biden then followed up: "First of all, is the answer yes?"

"The answer is absolutely yes, Joe," Harris said. "And I am ready to work, I am ready to do this with you, for you, I am just deeply honored and I am very excited."

A historic pick

Harris' rise is both historic and conventional. She now becomes the first woman of color to be on a major party ticket, the daughter of Jamaican and Indian immigrants, in a history-making decision that Biden wanted -- and was pushed -- to make by a range of people close to him.

"I've stopped crying for the moment," said Leah Daughtry, a longtime Democratic operative who urged Biden to pick a black woman as his running mate. "I am glad to see that what the vice president said on the road, about wanting a ticket that looks like America, is exactly what he did."

Daughtry had a slight heads up that Harris would be the pick. But it was when she saw the news on television, with a black woman being presented as her party's vice presidential nominee, that she "screamed and then just started crying."

But as momentous as Harris' pick is, in the long history of American vice presidential candidates, it was also widely seen as the most obvious pick for months, with speculation beginning even when she bowed out of the presidential race earlier this year.

Biden, throughout the process, used his friends and longtime advisers as a sounding board. And none more than former President Barack Obama.

A person close to the vetting process tells CNN that Biden and Obama spoke regularly about the choices before him and the political moment facing the country.

The former president "did not put his thumb on the scale for any particular candidate," the person close to the process said, "but mostly provided high-level counsel" as the former vice president worked through his decision.

And there are echoes of Obama's decision to pick Biden in the current presumptive Democratic nominee's pick of Harris. One of the reasons Obama selected Biden 12 years ago was that Biden had been tested on the national stage. It was that same quality that also played a critical role in Biden choosing Harris, given her experience as a presidential candidate in the 2020 primary, and that their ticket would reflect the diverse tapestry of America.

Biden viewed running for president as "the ultimate test," said an adviser, and believed Harris was "prepared and ready to be president" because of it.

"That was a big factor," the adviser said.

A Biden friend said the former vice president took a deep look at nearly a dozen women in his search and Harris "always made sense to him."

Terry McAuliffe, the former governor of Virginia, said Biden made clear in multiple talks with him over the last year that, more than anything, he wanted preparedness in a running mate. And as Biden's decision neared, McAuliffe said the former vice president kept reiterating that he wanted to pick someone who signaled that he, as president, would put together a "top shelf" administration.

"To me," McAuliffe said, "she fit all the things he was looking for and I have felt that over the last year and a half."

Biden's search was deliberate as the former vice president looked for a governing partner and a loyal teammate. People close to him said he would often keep his cards close to his chest on his eventual pick, out of respect for all the women in the running.

A bruising campaign

Throughout the process, Biden talked often about the bruising nature of a presidential race, particularly the general election campaign ahead with Trump, and he believed experience was critical. That contributed to Biden beginning -- and ending -- his search with Harris.

Harris always being a leading candidate isn't to say there weren't issues along the way, the most notable being how the people close to Biden -- including some of the vetting team -- felt about the fiery debate clash in June 2019, which Jill Biden later described as being "like a punch to the gut."

The moment was the high point of Harris' otherwise lackluster primary campaign and provided her with an early jolt.

Inside Biden's campaign, though, many were shocked, none more than the vice president himself, who days later told CNN that the attack stunned him because it was coming from Harris, someone who he believed he had a bond with because of their shared relationship with Beau Biden, the vice president's late son.

"She knew Beau," Biden said in an interview with CNN when asked about the attack. "She knows me."

Biden often refers to Beau, who died of brain cancer in 2015, as his soul. But Harris was close to the former Delaware Attorney general, too, with the two becoming friends during a fight with national banks during the foreclosure crisis in the 2000s.

In his note to supporters on Tuesday, Biden made clear that his decision was guided by his late son's view of Harris.

"He had enormous respect for her and her work," Biden said. "I thought a lot about that as I made this decision. There is no one's opinion I valued more than Beau's."

Yet the debate attack again became a flashpoint in the vetting process, when Politico reported in July that former Sen. Chris Dodd, a member of Biden's search committee, was taken aback when he asked Harris about the attack and she reportedly said, "That's politics."

"She had no remorse," a flabbergasted Dodd reportedly told a Biden supporter.

The onslaught of criticism set off alarm bells among Harris supporters like Eleni Kounalakis, the lieutenant governor of California and longtime Harris friend, who told CNN that when Harris recently started to receive criticism, she helped organize a video conference call with Biden's selection team that included California elected and labor leaders.

The Harris allies each took turns and vouched for Harris to all four members of Biden's search committee, including Dodd. According to Kounalakis, Dodd thanked everyone for doing the call, and reassured them that he knows Harris well and that he thought very highly of her.

Throughout it all, Kounalakis said, Harris remained calm.

"I wasn't worried for her because she kept telling me, 'whatever happened it was going to be fine.' She was very zen about the whole process and she did not want a campaign to put pressure on the vice president," she said. "She was very clear that she wanted the job, but she would wait and respectfully let him make his choice."

And Biden, in a direct contrast to Trump, wanted the public to know that he didn't hold a grudge against her.

During a press conference shortly after the report regarding Dodd, the former vice president was photographed with notes in his pocket that pointed to Harris as a top pick.

"Do not hold grudges," the notes read. "Campaigned with me & Jill... Great help to campaign... Great respect for her."

That moment, said people close to Harris, was when many close to her believed she could be the pick.

And, McAuliffe said, it showed Biden wanted someone who was "an independent voice who is willing to speak up."

"What," the former governor said, "a contrast to Trump."