US Senator Bernie Sanders said he will seek the Democratic Party presidential nomination in 2020.
The 77-year-old made the announcement in an email to supporters asking for 1 million people to sign up to start the effort.
"Our campaign is about creating a government and economy that works for the many, not just the few," Sanders said.
The senator from Vermont has been among the leaders of prospective 2020 candidates in opinion polls.
Sanders has been a critic of President Donald Trump in the past and called him "the most dangerous president in modern American history" in his email.
"We are running against a president who is a pathological liar, a fraud, a racist, a sexist, a xenophobe, and someone who is undermining American democracy as he leads us in an authoritarian direction," Sanders said.
The progressive populist mounted a fierce challenge to front-runner Hillary Clinton in the 2016 election.
Who else is in the Democratic race?
Already in the Democratic race are fellow Senators Cory Booker of New Jersey, Kamala Harris of California, Kirsten Gillibrand of New York, Amy Klobuchar of Minnesota, and Elizabeth Warren of Massachusetts.
"Together, you and I and our 2016 campaign began the political revolution. Now, it is time to complete that revolution and implement the vision that we fought for," Sanders said.
What's he pushing for?
Sanders is a political independent and democratic socialist. He said he would push for universal healthcare, raise the minimum wage and provide free public college tuition. He’s using the same issues from his 2016 campaign which resonated with younger voters.
"Three years have come and gone. And, as a result of millions of Americans standing up and fighting back, all of these policies and more are now supported by a majority of Americans," he said.
Sanders was a former mayor of Burlington in Vermont. He won a US House of Representatives seat in 1990 and then became the first independent at the house in 40 years.