(CNN) — Joe Biden is thinking big.

Confronted with the prospect of taking office next year in the depths of a historic economic and health crisis, Biden is now talking about a bolder presidency, with ambitions stretching beyond the restoration of pre-Donald Trump normalcy.

And there is a growing sense in Democratic circles, particularly among the progressive wing of the party, that there is one sure way to show he means it: Make Elizabeth Warren his running mate.

The Massachusetts senator has mostly been regarded as a vice presidential dark horse more likely destined, if progressive dreams were answered, for a top cabinet position. But that calculation could be shifting as the factors influencing Biden’s decision evolve in the face of a mushrooming catastrophe. Over the past month, the pair have forged a deeper personal connection, following the death of Warren’s brother, and begun to sharpen their focus on common political ground as Biden publicly shifted on an issue that famously divided them nearly two decades ago.

Biden spent much of the Democratic primary locked in on a pledge to revive decency in American political culture. Warren ran on a call for “big, structural change” that launched her to the top of the polls in the summer of 2019, but didn’t translate into success this year. The heart of Biden’s appeal remains steady, but as the coronavirus fallout deepens, he has also begun to telegraph a desire to strike out with a more ambitious policy agenda — a political enterprise, in scope and scale, that many Warren allies believe she is uniquely qualified to shepherd through the mazy, grinding gears of government.

That the possibility of sharing a ticket remains after a primary in which the two occasionally clashed in direct and personal terms is another marker of the fluidity of the race.

In November 2019, Warren responded to Biden’s criticism of her “Medicare for All” plan by accusing him of “repeating Republican talking points” and suggesting the former vice president, given his position on the matter, might be “running in the wrong presidential primary.” Biden struck back in an unusually blunt Medium post, calling out Warren — though not by name — for taking a “my way or the highway approach” he described as “condescending to the millions of Democrats who have a different view.”

But that episode resonates now only as an outlier, a rare — and brief — bare-knuckle brawl in a contest that saw so few of them. Since Warren dropped out in March, she has been full of praise for Biden. His “decency,” she told MSNBC’s Rachel Maddow in an interview after she left the race, “comes through in pretty much everything he does.”

Earlier this week, Biden tweeted a video of the pair teaming up to call and thank a small dollar donor — a personal touch employed by the Massachusetts senator during her own campaign.

“I used to call my contributors,” Biden tells a supporter in the clip, “but I never had as many until (Warren) endorsed me.”

Warren, too, has been moved by the former vice president’s efforts — in particular his March decision to endorse Warren’s consumer bankruptcy reform plan, which opens up new avenues for student debt relief. It had been a bone of contention between them tracing back decades, to when they famously squared off over it during a hearing on Capitol Hill. A source familiar with Warren’s thinking said it meant a lot to her that Biden adopted her bankruptcy plan when she dropped out.

Still, Biden’s decision-making process is expected to stretch on for weeks, if not months. And even as he and Warren come together on some hot button issues, there are still significant political gaps to bridge between the moderate stalwart and progressive icon. Warren is widely regarded as a “team player,” but the degree to which Biden is willing to hand over significant power to an ideological rival, and what Warren is willing to concede in order to strike a partnership, remains an open question.

A more personal connection

The question that hangs over this springtime surge of interest in Warren’s prospects more frequently turns on whether she and Biden have — or are on their way to making — the kind of personal connection he wants in running mate.

A source familiar with the Biden-Warren relationship acknowledged that the pair doesn’t necessarily “get along like they are friends,” but said both believe that the other is in politics “for the right reasons.”

“I would argue they very much are simpatico,” the source said, channeling a term Biden himself has often used when talking about the decision. “Personal relationship is part of it. But how you view the world is, too.”

That potential connection, though, has grown in recent weeks — as the senator mourns her brother, Donald Reed Herring, who died of Covid-19. Warren described the conversation she had with Biden, who called to offer his condolences, in a recent interview with The Atlantic.

Biden contacted Warren shortly after her brother’s death, the source said. Speaking to The Atlantic, she described the exchange that followed as “one person who’d lost loved ones trying to console another person who just lost her beloved brother.” A source familiar with their discussions said Warren and Biden have now spoken several times since Warren dropped out of the race, both before and after her brother died.

Warren has been on the other end of similar calls.

Murshed Zaheed, a former aide to former Senate Majority Leader Harry Reid and progressive operative who has become one Warren’s most vocal outside backers, recalled his phone ringing on the morning of his father’s funeral, in March of 2018.

“She talked to me and I can’t quite put into words how powerful that stuff is,” Zaheed said. “And then she called me a year later, on the anniversary of dad passing away. So when I read the story about Biden and Warren connecting over grief — that’s powerful. That’s a bond that you can’t quite explain.”

“I saw that paragraph (in the Atlantic) and it hit me right then,” he said. “It’s like, ‘OK, not everybody’s going to pick up on it, but that’s not lip service, that stuff matters.’ And that creates a different kind of chemistry.”

The Biden campaign has been tight-lipped about its process, and keeps a shorter shortlist than one might ascertain from public pronouncements and appearances, which seem to oscillate among the contenders. Asked why she sensed an increased opening for Warren, Sara Nelson, the international president of the Association of Flight Attendants, pointed to a specific moment Biden and his team chose to highlight.

“I’m seeing actions that show it,” said Nelson, an increasingly influential labor leader. “The grilling that Elizabeth Warren gave Steve Mnuchin (on Tuesday) around enforcement of the CARES Act … was right in line with what we were talking about. Biden picked that up and amplified it with a tweet thread.”

Richard Cordray, the first director of the Warren-built Consumer Financial Protection Bureau, who has worked closely with her and Biden, told CNN he believed a new economic crisis — and prospect that it could linger for years without significant interventions — raised Warren’s stock.

He also suggested that, for all the policy differences they sparred over during the primary, Biden and Warren had more in common than many realized.

“Both of them have a tremendous personal strain to their policy. They really do see policy in terms of, for Biden, in terms of his middle class upbringing, and the same really for Elizabeth,” Cordray said. “And it’s something that neither of them has ever lost through many years in the public arena. A lot of people do kind of move on from their roots, but neither of them ever has.”

The coronavirus effect 

“The crisis has clearly changed things,” said Rep. Ro Khanna, a former co-chair of Sen. Bernie Sanders’ campaign who wrote an op-ed last week making the case for Biden to choose Warren as his running mate. “It calls for bold, structural programs. That argument was harder to make when we were at 3.5% unemployment.”

Other Warren allies pointed to her turn as a pre-pandemic Cassandra, whose warning in the summer of 2019 that the economy was one “shock” away from another collapse were mostly ignored. When she offered a series of plans, earlier this year, for dealing with the coronavirus when its full force was unleashed on the country, those too were largely overlooked.

“It was Elizabeth Warren back in January who had a plan for coronavirus. No one else was talking about that then,” said Rebecca Katz, a progressive political strategist. “She had a plan about the health crisis around the coronavirus and a plan about the economic crisis. Imagine if we actually did what she advised in the plans a few months ago — where we would be right now?”

Katz also pointed to the political brand that Warren brings to the contest, the one that helped elevate her to the top of the primary field for a time last year, when she led in the polls as Democrats embraced her as the candidate with a “plan” for everything.

“You don’t have to make that a new message,” Katz said. “Warren ran on having a plan and that is something that broke through and people know that about her a year later. It is not abstract.”

Biden and his team have said that the decision will ultimately turn on two key wagers: that he can foresee a partnership, in the White House, that has the potential to mirror the close relationship he shared with President Barack Obama. And that his choice be ready to ascend and lead, if necessary, with little or no on-the-job training.

Warren’s ability to step seamlessly into the role — and take the step up if necessary — is unquestioned by most Democrats.

“I don’t claim to know who (Biden) is going to select, but as far as I’m concerned, I think he should go for someone who has the qualifications necessary to serve as vice president,” said Jim Manley, a longtime aide to Reid. “And I’m not convinced everyone being discussed meets that criteria.”

As for Warren?

“Very much so. I mean, she’s a one-woman policy shop!” Manley said. “She obviously has the policy chops, but possibly more importantly, she knows how to move the levers of power within the regulatory process to get things done.”

A recent CBS News Poll suggests that Warren would be a popular choice with a large swath of Democratic voters. More than 7-in-10 respondents said she should be considered for the slot. Sen. Kamala Harris was her closest competition, with 59%. Fifty percent named former Georgia gubernatorial candidate Stacey Abrams and 49% listed Sen. Amy Klobuchar.

Pitted against each other, Warren came out on top again, with 36% naming her as their first choice. Harris placed second at 19%. Abrams and Klobuchar again finished third and fourth, respectively.

A CNN national poll earlier this month found Warren was viewed favorably by 69% of Democratic voters and unfavorably by 19%.

Warren allies shape their case

Progressives have been, for varying reasons, hesitant to publicly plump too hard for Warren.

Sanders has passed up the opportunity, in public and private, to make her case to the Biden team. His longtime senior adviser Jeff Weaver also demurred, saying he was taking “the same position as Bernie Sanders, which is: that’s a decision (Biden) has to make for himself.

But Weaver, who recently launched a super PAC to support Biden, echoed other leading progressive voices with his specific praise.

“Senator Warren has had a long history of being very focused on personnel as a means of effectuating progressive change,” he told CNN. “And obviously that’s would be an incredibly valuable skill in the administration.”

Choosing Warren would also help Biden with his small dollar fundraising, cut down on potential grumbling from progressives skeptical of his commitment to engaging their ideas and potentially inspire Warren’s considerable grassroots support to become more active in the campaign.

“Reducing the sort of negative earned media from ‘Bernie or bust’ type of voters, because she is the overwhelming preference of Bernie supporters, while also helping entrench those gains in suburbs, is an asset,” said Sean McElwee, co-founder of Data for Progress, a progressive think tank and pollster.

But like so many others Warren allies, McElwee returned to the competence argument, a framing designed to appeal across both the party and country’s ideological divisions — and, in the event Democrats win, position them to make immediate use of their new power.

“To ensure that we keep the House in 2022, (Biden) needs to deliver immediate and visible benefits to working class and middle class Americans,” McElwee said. “And that means you have to take the ship of government that has been utterly wrecked by Republicans and rebuilding it in a way that can actually deliver benefits to people.”

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