Bernie Sanders, the independent senator from Vermont whose 2016 presidential campaign helped energize the progressive movement and reshaped the Democratic party, has entered the 2020 race for the White House.

Sanders, a self-styled democratic socialist who spent much of his nearly 30-year congressional career on the political fringe, cast his candidacy as the best way to accomplish the mission he started three years ago when he ran against Hillary Clinton for the Democratic nomination.

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“Together, you and I and our 2016 campaign began the political revolution,” he said in an email announcing his decision to supporters on Tuesday morning. “Now, it is time to complete that revolution and implement the vision that we fought for.”

Sanders, 77, running as a Democrat again, believes he can prevail in a crowded and diverse field that includes several female and minority candidates, and then beat Donald Trump, whom he called on Tuesday “the most dangerous president in modern American history”.

Asked in an interview on CBS on Tuesday morning what would be different about his 2020 campaign, Sanders replied: “We’re gonna win.”

Whether he can once again capture grassroots support, and whether the energy of his past campaign will pass to other candidates, will likely be a central factor in determining who Democrats nominate to take on the sitting president.

The progressive policies Sanders helped popularize in 2016 – Medicare for All, a $15-an-hour federal minimum wage, tuition-free college, demands to fight climate change more aggressively and to tax the wealthy at a higher rate – have now been broadly embraced by several other presidential candidates.

Sanders wrore: “Three years ago, during our 2016 campaign, when we brought forth our progressive agenda we were told that our ideas were ‘radical’ and ‘extreme’. Well, three years have come and gone. And, as result of millions of Americans standing up and fighting back, all of these policies and more are now supported by a majority of Americans.”

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Sanders will face opposition from moderate Democrats and from Republicans who are likely to use his candidacy to paint the party as too liberal. In a preview of Trump’s re-election campaign, the president used his State of the Union speech this month to warn against what he said was the creep of socialism in America.

Trump 2020 campaign spokeswoman Kayleigh McEnany said in a statement: “Bernie Sanders has already won the debate in the Democrat primary, because every candidate is embracing his brand of socialism.

“But the American people will reject an agenda of sky-high tax rates, government-run health care and coddling dictators like those in Venezuela. Only President Trump will keep America free, prosperous and safe.”

Sanders made clear on Tuesday that he plans to go after Trump directly in his campaign.

In an interview with Vermont Public Radio, where he first announced his bid, he said: “I think the current occupant of the White House is an embarrassment to our country. I think he is a pathological liar. 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.”

After a midterm election cycle that saw women and minority candidates sweep to power, the nominating contest is likely to be fought not only over ideology but over identity and electoral strategy. Already, the 2020 candidates are being pushed on how they can appeal to the Democrats’ broad range of demographic groups, which includes working-class families, black and Latino voters, suburban women and young people.

This year, Sanders apologized publicly and privately to former female staffers after allegations of sexual harassment by male staffers on his 2016 campaign. He has also continued to stumble on questions about race, despite a years-long effort to improve his standing with minority voters.

Still, no candidate will enter the race with as many advantages as Sanders, who ended the 2016 primary with more than 13m votes and nearly $230m raised, much of it through small donations. Now he begins a second run not as a political outsider but as a top-tier candidate with near-universal name recognition, a dedicated following and an unrivaled donor list.

Yet he will likely face far greater scrutiny, in a growing field already populated by colleagues and allies including the Massachusetts senator Elizabeth Warren, his closest friend in Congress.

Senators Kamala Harris of California, Cory Booker of New Jersey, Kirsten Gillibrand of New York and Amy Klobuchar of Minnesota have all entered the race, as have lower-profile contenders including the former San Antonio mayor and federal housing secretary Julián Castro and Pete Buttigieg, the young mayor of South Bend, Indiana.

The former vice-president Joe Biden, former Texas congressman Beto O’Rourke and billionaire businessman Michael Bloomberg are all weighing whether to run.

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With a fractured Democratic field, advisers believe Sanders’ core support, should he retain it over the next year, will be enough to power his campaign in the Iowa caucuses and New Hampshire primary, the early voting states that helped lift his 2016 campaign.

He is likely to benefit from a campaign waged by his allies to reform the party’s primary process, which succeeded in stripping voting power from the so-called “superdelegates”, a major source of controversy in 2016 when Sanders lost the battle for the nomination to Clinton.

Born to Jewish parents with roots in Poland and Russia, Sanders grew up poor in a cramped apartment in Brooklyn, New York. He graduated from the University of Chicago, where he became involved in the civil rights movement. In 1981, he was elected mayor of Burlington, Vermont. In 1990, Sanders became the state’s sole representative in Congress, where he served until he joined the Senate in 2006.

Following the election of Trump, Sanders published a book titled Our Revolution: A Future to Believe In. He has four children and is married to Jane O’Meara, a former president of Burlington College and his closest adviser.