All news on the topic: Endorsement

The Massachusetts senator is the last of Biden's major Democratic rivals to endorse him, holding out longer than fellow progressive Sen. Bernie Sanders.

"He’ll show there’s more that unites us than divides us," the New Jersey Democrat, who quit the presidential race in January, said of Biden.

Castro, who quit the Democratic race this month, said Warren is "unafraid to fight like hell to make sure America’s promise will be there for everyone."