Sen. Bernie Sanders (I-VT), a progressive who ran a formidable campaign for President of the United States in 2016, but ultimately lost to Democrat primary rival Hillary Clinton, announced Tuesday morning he is launching a second run for the White House in 2020.

I'm running for president. I am asking you to join me today as part of an unprecedented and historic grassroots campaign that will begin with at least 1 million people from across the country. Say you're in: https://t.co/KOTx0WZqRf pic.twitter.com/T1TLH0rm26 — Bernie Sanders (@BernieSanders) February 19, 2019

“Our campaign is not only about defeating Donald Trump,” the 77-year-old self-described democrat socialist said in an email to supporters. “Our campaign is about transforming our country and creating a government based on the principles of economic, social, racial and environmental justice.”

Sanders, who enthusiastically embraces proposals ranging from Medicare for All to free college tuition, stunned the Democrat establishment in 2016 with his spirited challenge to Clinton. While she became the party’s nominee, his campaign helped lay the groundwork for the leftward lurch that has dominated Democratic politics in the Trump era.

Still, there is no question that Sanders will be a strong contender for the Democratic nomination. He won more than 13 million votes in 2016 and dozens of primaries and caucuses. He opens his campaign with a nationwide organization and a proven small-dollar fundraising effort.

In a Tuesday morning interview with CBS This Morning, Sanders said it is “absolutely imperative that Donald Trump be defeated” because his presidency is “un-American.”

“It is absolutely imperative that Donald Trump be defeated because I think it is unacceptable and un-American, to be frank with you, that we have a president who is a pathological liar and it gives me no pleasure to say that, but it’s true,” the lawmaker told interviewer John Dickerson. “We have a president who is a racist, who is a sexist, who is a xenophobe, who is doing what no president in our lifetimes has come close to do doing, and that is trying to divide us up,” Sanders added.

He said he was going to launch “what I think is unprecedented in modern American history”: a grassroots movement “to lay the groundwork for transforming the economic and political life of this country.”

“All of those ideas people were saying, ‘Oh Bernie, they’re so radical. They are extreme. The American people just won’t accept those ideas,’” said Sanders. “Well, you know what’s happened in over three years? All of those ideas and many more are now part of the political mainstream.”

One of the biggest questions surrounding Sanders’ candidacy is how he will compete against someone like Sen. Elizabeth Warren (D-MA), who shares many of his policy goals. Warren has already launched her campaign and has planned an aggressive swing through the early primary states.

The growing Democrat presidential field also includes Sens. Kamala Harris (D-CA), Cory Booker (D-NY), Kirsten Gillibrand (D-NY), Amy Klobuchar (D-MN), and Obama-era HUD Secretary Julian Castro. Former Vice President Joe Biden and former Rep. Robert Francis “Beto” O’Rourke (D-TX) are also mulling White House bids of there own.

A recently released poll via the Saint Anselm College Survey Center at the New Hampshire Insititute of Politics, said Sanders, Biden, and Harris are most favored by New Hampshire voters ahead of the 2020 Democrat presidential primary.

Breitbart News’ Kyle Morris reported:

Of the 600 surveyed, 258 respondents indicated they would vote in the primary. The phone survey then presented them with names of those running for the Democratic presidential nomination, or those that have indicated that they are strongly considering it, and asked them to give their impression of each. Of the 14 names listed, former Vice President Biden had the highest favorability at 80 percent, while Sanders notched 65.3 percent.

A Morning Consult poll published last week shows Biden and Sanders leading the pack of White House hopefuls.

Biden topped the list of contenders with 29 percent from likely voters, while Sanders garnered 22 percent.

While Sanders had been working to lay the groundwork for a second campaign for months, it was unclear whether he will be able to expand his appeal beyond his largely white base of supporters. In 2016, Sanders notably struggled to garner support from black voters, an issue that could become particularly pervasive during a primary race that could include several non-white candidates.

Sanders also faces different pressures in the #MeToo era. Some of his male staffers and supporters in 2016 were described as “Bernie bros” for their treatment of women.

In the run-up to Sanders’ 2020 announcement, persistent allegations emerged of sexual harassment of women by male staffers during his 2016 campaign. Politico and The New York Times reported several allegations of unwanted sexual advances and pay inequity.

Robert Becker, who managed Sanders’ Iowa campaign, was accused of forcibly kissing a young female staffer during the Democrat National Convention. The top Sanders aide allegedly told the unidentified female staffer in her 20s that he wanted to have sex with her, making a reference about riding his “pole,” three other individuals who say they witnessed the incident or were told about it moments later by those who saw it. Hours later, Becker is said to have abruptly grabbed the woman’s wrists and forcibly kissed her, shoving his tongue in her mouth.

In an interview with CNN after the initial allegations surfaced, Sanders apologized but also noted he was “a little busy running around the country trying to make the case.”

“I am not going to sit here and tell you that we did everything right in terms of human resources, in terms of addressing the needs that I am hearing from now that women felt disrespected, that there was sexual harassment, which was not dealt with as effectively as possible,” 2020 candidate told host Anderson Cooper.

As additional allegations emerged, he offered a more unequivocal apology.

“What they experienced was absolutely unacceptable and certainly not what a progressive campaign — or any campaign — should be about,” Sanders told reporters on Capitol Hill. “Every woman in this country who goes to work today or tomorrow has the right to make sure that she is working in an environment which is free of harassment, which is safe and is comfortable, and I will do my best to make that happen.”

In a statement emailed to Breitbart News, Republican National Committee spokesperson Michael Ahrens said of the Independent Vermont senator’s bid: “Bernie Sanders is a self-avowed socialist who wants to double your taxes so the government can take over your health care. The vast majority of voters oppose his radical agenda, just like they are going to oppose all the 2020 Democrats who have rushed to embrace it.”

The Associated Press contributed to this report.