Biden has told supporters and former staff that he will run, according to one source who has knowledge of discussions. Biden and his aides also have reached out to donors and potential bundlers - people who volunteer to raise money on behalf of the candidate - to assess support, according to another source. A third source with direct knowledge of Biden's plans offered a caveat, saying the former vice president was very close to running, but "it's not 100 percent." 'We're leaning into that moment' when Biden gives the green light, the source said.