Sanders argues his record of defending Social Security makes him the best Democratic primary candidate to defeat the president in November.
Sanders had previously held off on endorsing Jessica Cisneros, who is challenging Democratic Rep. Henry Cuellar from the left.
Organize for Justice has initiated a $500,000 digital campaign against Biden and former South Bend, Indiana, Mayor Pete Buttigieg.
The mailer, picturing Iranian soldiers, clerics and government officials, says, "We live in the most dangerous moment in a generation.”
Wisconsin Rep. Mark Pocan says Rep. Joe Kennedy III and Sen. Ed Markey have virtually indistinguishable ideologies.
Former Ohio state Sen. Nina Turner faulted Democratic presidential rival Elizabeth Warren for responding to a dispute with Bernie Sanders.
The initiative shows a united progressive front against the centrist candidates amid a fight between Bernie Sanders and Elizabeth Warren.
Tuesday’s presidential debate could see a clash between the left-wing leaders — and a win for Joe Biden.