Bernie Sanders announces he's running for president again in 2020

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Bernie Sanders, then a Democratic presidential candidate, speaks at a rally at the University of Massachusetts in Amherst in 2016.

• Sen. Bernie Sanders on Tuesday announced he's running for president in 2020.
• Sanders' 2016 presidential campaign made him a household name, despite the fact he ultimately lost to former Secretary of State Hillary Clinton.
• The ghosts of the 2016 primary season may continue to haunt Sanders in 2020, but he also remains one of the most popular politicians in the country.

Sen. Bernie Sanders on Tuesday announced he's running for president in 2020.

Sanders, an independent who caucuses with the Democrats, ran for the Democratic nomination for president in 2016. He ultimately lost to former Secretary of State Hillary Clinton, but went from being a relatively obscure political figure to a household name along the way.

His 2016 campaign shocked much of the country, as no one expected him to pose a significant challenge to Clinton at the start. But his populist platform and matter-of-fact style of speaking, along with his thick Brooklyn accent, won over a significant cohort of voters.

He told Vermont Public Radio that he is seeking the 2020 Democratic presidential nomination.

"I wanted to let the people of the state of Vermont know about this first," he said. "And what I promise to do is, as I go around the country, is to take the values that all of us in Vermont are proud of - a belief in justice, in community, in grassroots politics, in town meetings - that's what I'm going to carry all over this country."

The Vermont senator was especially popular with young voters in 2016, garnering more votes from this demographic than either of the two major-party presidential nominees combined.

But he struggled to win over the Democratic establishment, and many dismissed his policy proposals as idealistic and unrealistic.

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Some supporters of Sanders accused the Democratic National Committee of rigging the primaries in Clinton's favor and robbing the election from him, though there's no concrete evidence to support this notion.

After a heated primary season, Sanders ultimately supported Clinton in her effort to defeat Donald Trump in the general election. Some Clinton supporters feel he should've conceded and dedicated his support to her earlier in the campaign season, and have pointed to Sanders as one of the reasons she ultimately lost the election.

Some of these issues might continue to haunt Sanders along the campaign trail in the upcoming presidential election, on top of sexual harassment allegations linked to his campaign.

Read more: Bernie Sanders campaign alumni want to address the sexual harassment they say took place in 2016 as he mulls another presidential run

The allegations were not directed at Sanders, but several women who worked on the campaign said they were harassed by staff members and also experienced pay disparities. Sanders has apologized for this, and claimed he was not aware of the allegations amid the campaign season.

Despite some of the obvious challenges Sanders will face moving forward, he remains one of the most popular politicians in the country.