"This campaign is about the needs of the American people and addressing the very serious crises that we face", he added. "And there is no doubt in my mind that, as we head into November, Hillary Clinton is far and away the best candidate to do that".
News of Mr. Sanders's endorsement of Mrs. Clinton follows developments that the Federal Bureau of Investigation (FBI) will not charge her for any alleged criminal activities stemming from her handling of classified government information on a private email server.
Sanders and Clinton pitched themselves as joining forces to defeat Donald Trump, with Clinton declaring, "We are stronger together!"
Just two weeks shy of the Democratic National Convention.
Throughout the primary season, Sanders led a highly engaged, progressive grassroots campaign. Sanders himself penned a heartfelt letter to supporters, acknowledging that he understands some of them may be "disappointed". While he mounted a surprising challenge for the Clinton campaign, the senator ultimately stood back for the sake of uniting the party against the presumptive Republican nominee, Donald Trump.
Trump himself got on social media to chastise Sanders for the endorsement.
Stein - who has always been a vocal critic of Clinton - disagreed, tweeting, "many Bernie hearts are breaking right now" and including an emoji of a breaking heart. She later went on to applaud him for all the he was able to accomplish with his campaign and thank his many supporters.
"You know what I like about Hillary?" said Pauline Raiche, of Brentwood.
Cheryl Marshall, a Sanders delegate from Columbia County, said Clinton will fight for such key issues as "raising the minimum wage, lowering the cost of college and making health care more affordable". "On Tuesday, Sanders finally offered Clinton his endorsement ..."