WASHINGTON — Former vice president Joe Biden called Senator Elizabeth Warren himself on Tuesday with the news: She would not be his running mate.
Biden’s choice of California Senator Kamala Harris was not a surprise, but it nonetheless was a blow to Warren’s vice presidential ambitions — she has all-but-openly campaigned for the slot for months — and a disappointment to voters on the left who hoped the Massachusetts liberal would give the Democratic ticket a progressive jolt.
And it raises the question of what role one of the most prominent progressives might play in a Biden administration, should he and Harris be elected: Would she be a key player inside Biden’s world, either as a Cabinet secretary or as an informal adviser? Or might she become an outside critic of an administration that is more moderate than she is, as happened at times during the Obama years?
“It’s clear she’s going to be very influential and important,” said former Massachusetts representative Barney Frank. “She is willing to be independent and differ, but she knows how to do that in ways that maximize her influence.”
Warren congratulated Harris on Tuesday, calling her “a great partner to Joe Biden in making our government a powerful force for good in the fight for social, racial, and economic justice.”
In the five months since Warren ended her own presidential bid, she has become an enthusiastic surrogate for Biden — as well as a fund-raising powerhouse. And she landed herself on Biden’s vice presidential short list, along with contenders like Harris, former national security adviser Susan Rice, and California Representative Karen Bass, and stayed there until Tuesday.
Crucially, she has also emerged as something of a policy adviser to Biden, speaking with her former primary rival by phone regularly since she dropped out of the race. Her imprint is apparent in his “Build Back Better” economic plan — which contains planks of Warren’s “economic patriotism” plan that was a trade proposal designed to increase US jobs — and in his embrace of the cancellation of some student loan debt and expansion of Social Security benefits.
“Warren will play a big role in laying out an economic agenda with a focus on the working class and middle class,” said Representative Ro Khanna of California, the former cochair of Vermont Senator Bernie Sanders’ campaign who came to back her for vice president. He added, “Whether from the senator or from the administration, she has the brilliance to help shape policy.”
Warren quickly became the favored vice presidential choice of progressive groups including the Working Families Party, which had backed her during the primary, as well as Sanders-supporting groups like Roots Action and the Progressive Democrats of America. They argued she could turn out young and left-leaning voters. But some Democrats worried she would turn off more moderate voters, while others saw her as an ill fit for a historic moment, in the wake of the George Floyd protests, that had led many in the party to urge Biden to choose a woman of color.
Some of her allies, like the Progressive Change Campaign Committee, which endorsed her presidential campaign, are strongly hinting that Biden needs to commit to putting liberals like her in his Cabinet if he wants progressive voters to feel excited about him on Election Day.
“His ambitious Build Back Better agenda, based on ideas from Elizabeth Warren and other progressive leaders, was a strong step toward increasing progressive enthusiasm — and the next will be ongoing evidence that Elizabeth Warren-style progressives will have a strong set of seats in a Biden-Harris Administration,” said a statement from the group.
Other Warren allies, including the progressive think tank Data for Progress, have already begun to explicitly make the case that she belongs in Biden’s Cabinet as his treasury secretary. She would be the first woman to hold that position.
But some of her supporters say they would prefer to see her tug a Biden administration to the left from the outside. They remember her oversight role after the 2008 financial crisis and how she publicly grilled then-treasury secretary Timothy Geithner about the Obama administration response. She also marshaled her own supporters to torpedo the nomination of Wall Street banker Antonio Weiss to the Treasury Department in 2014 and launched an aggressive campaign to push the Obama administration to crack down on for-profit colleges.
“I’d probably rather she stay in the Senate, where she could be a stronger ally that doesn’t always have to toe the administration’s line,” said Charles Chamberlain, the executive director of Democracy for America. “She might be more powerful in the Senate than as treasury secretary.”
Jorden Giger, a board member of the Sanders-aligned group Our Revolution and an activist with Black Lives Matter in South Bend, Ind., also urged Warren to hold onto her “bully pulpit” in the Senate.
“She can challenge [Biden’s] administration to take bold, progressive steps and push for structural change,” he said.
Warren has long been adept at working the machinery of government and building consensus from the inside while also drawing on her supporters outside Washington — and her supporters expect she will continue to do that, no matter what formal role she takes next year.
“If there’s anyone I trust to actually play the inside-outside game, it’s Elizabeth Warren,” said Nelini Stamp, of the Working Families Party.
Frank does not think Warren should be Treasury secretary because he believes financial institutions would resist her even on small changes. But he said the national political climate has changed since the Obama years, and he believes Biden and Warren — with her likely still in the Senate — can form a partnership to address pressing issues like inequality.
“I think she’ll be taking a lead more in helping formulate how you address the issue than insisting that you address it,” Frank said. “She’ll still be pushing but she’ll be pushing on a door that’s more open.”
Jess Bidgood can be reached at Jess.Bidgood@globe.com. Follow her on Twitter @jessbidgood.