Warren left the race without endorsing Biden or her fellow progressive Senator Bernie Sanders — but the dynamics changed substantially in subsequent weeks, with campaigning forced into a hiatus amid the coronavirus outbreak.
Sanders dropped out last week and endorsed Biden within days, hoping to persuade his fervent progressive supporters to warm to the more centrist Biden.
Former President Barack Obama followed suit yesterday.
Warren's formal backing doesn't carry the political heft it might have if she had endorsed Biden over Sanders weeks ago.
Nonetheless, her announcement now could fuel speculation that Biden may choose her as a running mate. Biden has said he soon will announce a committee to oversee his vice-presidential search.
Warren made no mention of that possibility in announcing her endorsement video, instead saying Biden "grew up on the ragged edge of the middle class."
That phrase that was a centrepiece of Warren's own campaign and referred to her own upbringing in Oklahoma.
Biden saluted Warren for the series of detailed policy proposals she released as a candidate and said he will count on her to help rebuild the economy once the threat of the coronavirus lifts.
"She helped set a high-water mark for what our politics can be at their best — authentic and service-oriented, focused on how we can deliver the most help to the most people," he said in a statement.
"I am proud to have Senator Warren in my corner for the fight ahead — not just as we work to defeat Donald Trump in November, but in the years to come, as we push through a bold and progressive policy agenda for the American people."
Warren referred to the pandemic more directly in a tweet.
"In this moment of crisis, it's more important than ever that the next president restores Americans' faith in good, effective government — and I've seen Joe Biden help our nation rebuild. Today, I'm proud to endorse @JoeBiden as President of the United States," she said.
Some of Warren's allies note that, in the days before her endorsement, Biden embraced some of the senator's plans to combat the coronavirus, including calls to cancel student debt and expand Social Security benefits during the crisis. He also has adopted a plan she promoted as a candidate to overhaul the nation's bankruptcy system.
In her video, Warren also referenced the pair's sometimes rocky relationship. They clashed in 2005, when Biden was a Delaware senator and Warren was a Harvard Law School professor and bankruptcy expert, during a congressional hearing over a bankruptcy bill. It was a scene that Biden, as vice president, recalled when he swore Warren into office eight years later.
"Joe Biden was there at the very moment I became a Senator," Warren said. "And when he did, he said 'you gave me hell! And you're gonna do a great job.'"
- AP
