Sen. Elizabeth Warren (D., Mass.) is now the only major former Democratic presidential candidate who has not endorsed former vice president Joe Biden, the presumptive party nominee.
Sen. Bernie Sanders (I., Vt.) endorsed Biden Monday after dropping out of the race less than a week earlier. Biden described Sanders as "the most powerful voice for a fair and more just America," and Sanders said the coronavirus crisis is a moment for the Democratic Party to unify behind Biden.
Warren, who withdrew from the presidential race shortly after Super Tuesday, tweeted her appreciation of Sanders after he dropped out of the race last week but has not mentioned Biden on her personal Twitter account since she suspended her campaign.
New York mayor Bill de Blasio, a former presidential candidate whose numbers were among the lowest in the field, has also not endorsed Biden. He announced his endorsement of Sanders in February and warned that Biden has not been sufficiently vetted to be trusted with defeating Trump in the general election.
De Blasio also called on Warren to endorse Sanders in March, tweeting that "our progressive movement needs [Warren] more than ever."
As speculation mounted, Warren said she would hold off on announcing an endorsement because she was focused on the coronavirus crisis. She said Sanders needed space to decide what to do next.
In an apparent appeal to Warren's supporters, Biden endorsed the Massachusetts senator's proposed plan to change the bankruptcy system.