
US Sen. Bernie Sanders speaks at a campaign rally in Chicago in March 2019. Sanders, an independent from Vermont, is the longest-serving independent in the history of Congress.

Sanders, right, leads a sit-in organized by the Congress of Racial Equality in 1962. The demonstration was staged to oppose housing segregation at the University of Chicago. It was Chicago's first civil rights sit-in.

Sanders takes the oath of office to become the mayor of Burlington, Vermont, in 1981. He ran as an independent and won the race by 10 votes.

Sanders, right, tosses a baseball before a minor-league game in Vermont in 1984. US Sen. Patrick Leahy, center, was also on hand.

In 1987, Sanders and a group of Vermont musicians recorded a spoken-word folk album. "We Shall Overcome" was first released as a cassette that sold about 600 copies. When Sanders entered the US presidential race in 2015, the album surged in online sales. But at a CNN town hall, Sanders said, "It's the worst album ever recorded."

Sanders reads mail at his campaign office in Burlington in 1990. He was running for the US House of Representatives after an unsuccessful bid in 1988.

In 1990, Sanders defeated US Rep. Peter Smith in the race for Vermont's lone House seat. He won by 16 percentage points.

Sanders sits next to President Bill Clinton in 1993 before the Congressional Progressive Caucus held a meeting at the White House. Sanders co-founded the caucus in 1991 and served as its first chairman.

Barack Obama, then a US senator, endorses Sanders' Senate bid at a rally in Burlington in 2006.

Sanders takes part in a swearing-in ceremony at the US Capitol in January 2007. He won his Senate seat with 65% of the vote.

Sanders chats with Dr. John Matthew, director of The Health Center in Plainfield, Vermont, in May 2007. Sanders was in Plainfield to celebrate a new source of federal funding for The Health Center.

Sanders speaks to reporters in 2010 about the Obama administration's push to extend Bush-era tax cuts. Three days later, Sanders held a filibuster against the reinstatement of the tax cuts. His speech, which lasted more than eight hours, was published in book form in 2011. It is called "The Speech: A Historic Filibuster on Corporate Greed and the Decline of Our Middle Class."

Sanders and US Rep. Jeff Miller, chairman of the House Committee on Veterans' Affairs, walk to a news conference on Capitol Hill in 2014. Sanders was chairman of the Senate Committee on Veterans' Affairs.

In March 2015, Sanders speaks in front of letters and petitions asking Congress to reject proposed cuts to Social Security and Medicare.

In July 2015, two months after announcing he would be seeking the Democratic Party's nomination for President, Sanders spoke to nearly 10,000 supporters in Madison, Wisconsin. "Tonight we have made a little bit of history," he said. "You may know that some 25 candidates are running for President of the United States, but tonight we have more people at a meeting for a candidate for President of the United States than any other candidate has."

Seconds after Sanders took the stage for a campaign rally in August 2015, a dozen protesters from Seattle's Black Lives Matter chapter jumped barricades and grabbed the microphone from the senator. Holding a banner that said "Smash Racism," two of the protesters -- Marissa Johnson, left, and Mara Jacqueline Willaford -- began to address the crowd.

Sanders shakes hands with Hillary Clinton at a Democratic debate in Las Vegas in October 2015. The hand shake came after Sanders' take on the Clinton email scandal. "Let me say something that may not be great politics, but the secretary is right -- and that is that the American people are sick and tired of hearing about the damn emails," Sanders said. "Enough of the emails, let's talk about the real issues facing the United States of America."

Sanders embraces Remaz Abdelgader, a Muslim student, during an October 2015 event at George Mason University in Fairfax, Virginia. Asked what he would do about Islamophobia in the United States, Sanders said he was determined to fight racism and "build a nation in which we all stand together as one people."

Sanders waves while walking in a Veterans Day parade in Lebanon, New Hampshire, in November 2015.

Sanders sits with rapper and activist Killer Mike at the Busy Bee Cafe in Atlanta in November 2015. That evening, Killer Mike introduced Sanders at a campaign event in the city. "I'm talking about a revolutionary," the rapper told supporters. "In my heart of hearts, I truly believe that Sen. Bernie Sanders is the right man to lead this country."

Comedian Larry David and Sanders appear together on "Saturday Night Live" in February 2016. David had played Sanders in a series of sketches throughout the campaign season.

Sanders and his wife, Jane, wave to the crowd during a primary night rally in Concord, New Hampshire, in February 2016. Sanders defeated Clinton in the New Hampshire primary with 60% of the vote, becoming the first Jewish candidate to win a presidential primary.

Sanders speaks at a campaign rally in Ann Arbor, Michigan, in March 2016. He won the state's primary the next day, an upset that delivered a sharp blow to Clinton's hopes of quickly securing the nomination.

Sanders speaks at a campaign event in New York's Washington Square Park in April 2016.

Sanders speaks at a rally in Santa Monica, California, in June 2016. He pledged to stay in the Democratic race even though Clinton secured the delegates she needed to become the presumptive nominee.

Sanders endorses Clinton at a rally in Portsmouth, New Hampshire, in July 2016.

Sanders addresses delegates on the first day of the Democratic National Convention in July 2016.

Sanders brings a giant printout of one of Donald Trump's tweets to a Senate debate in January 2017. In the tweet, Trump had promised not to cut Social Security, Medicare and Medicaid.

Sanders thanks supporters after winning re-election to the Senate in November 2018.

Sanders looks at his notes as he watches President Trump deliver the State of the Union address in February 2019. That month, Sanders announced that he would be running for president again.

Sanders hugs a young supporter during a campaign rally in Los Angeles in March 2019.

Sanders addresses the audience at a CNN town hall in Washington in April 2019.