Not only is he the most popular Senator in the country, but recent polls also show he would pip Donald Trump in a hypothetical election. Some of his male staffers and supporters in 2016 were described as "Bernie bros" for their treatment of women. The explanation fell flat and, days later another report emerged accusing an operative on the campaign of forcibly kissing a younger female staffer.
Sanders aggressively challenged Hillary Clinton for the Democratic nomination in 2016, and his focus on economic populism has helped shift the party leftward, as is evident as the field of 2020 candidates emerges.
Sanders has been ranked among the leaders in opinion polls of prospective 2020 candidates, but he faces challenges from a large pool of other progressives who advocate for numerous same issues that he brought into the party's mainstream.
Despite coming in second in 2016, Sanders could emerge as the Democratic Party's frontrunner in 2020.
One of the biggest questions surrounding Mr Sanders' candidacy is how he will compete against someone like Ms Warren, who shares many of his policy goals. In his CBS interview, he noted that he is a member of the Democratic leadership and caucuses with the party, but said that the party needed to reach out to those who don't identify with a party.
He also highlighted policies he will advocate on the campaign trail: healthcare for all, raising the minimum wage to a "living wage", and combatting climate change. I believe people are entitled to get the best education they can. "My views are maybe a little bit different".
Mr Sanders galvanized a broad coalition with his anti-Wall Street rhetoric and talk of a "political revolution".
Harris distanced herself from Sanders on Tuesday.
Republican-Controlled Senate to Vote on Democrats' Green New Deal
Trump, at his rally Monday night, said that under the Green New Deal, "You're not allowed to own cows anymore". A copy of the new legislation published on Ocasio-Cortez's website was pulled off very soon after.
"You know as well as I do that we are living in a pivotal and risky moment in American history", he wrote.
"I also think he is a racist, a sexist, a homophobe, a xenophobe, somebody who is gaining cheap political points by trying to pick on minorities, often undocumented immigrants", Mr Sanders said.
Senator Sanders's successes in 2016 capped an unlikely political ascent.
But Sanders insisted his 2020 bid would not make the same mistakes: "We are going to have the strongest protocols to protect women and anybody else against any form of harassment".
But, hey - everything old is new again! He won a US House of Representatives seat in 1990 and then became the first independent at the house in 40 years. Liberal groups had launched efforts to draft Warren, although she chose not to run. After telling supporters during his New Hampshire primary victory speech that the average donation to his campaign was $27, the amount became rallying cry for his backers. By the summer of 2015, he was regularly speaking to crowds numbering in the thousands or tens of thousands.
The first major test of the Sanders movement came in 2018, when several progressive candidates made policies backed by Sanders a central part of their campaign.
His entry also may further highlight tensions between the more populist wings of the Democratic party and of moderates, as it did during the 2016 election.
"He's not so much out there on the left flank as he was", she said.