Sen. Bernie Sanders, I-Vt., a progressive who has two failed presidential runs under his belt, will try to convince his far-left supporters to embrace presumptive Democratic nominee Joe Biden at the Democratic National Convention on Monday night.

BERNIE SANDERS' CNN INTERVIEW INTERRUPTED REPEATEDLY BY SKYPE RINGTONE

Sanders has a 10 p.m. ET speaking slot on Monday, the first day of the mostly virtual Democratic National Convention. Milwaukee, Wis., had been preparing to host (and reap the rewards of) the convention that was expected to draw tens of thousands of people before the coronavirus pandemic hit.

Here are five things to know about Sanders:

1. He has a complicated history with the DNC

Sanders supporters and President Trump alike have accused the DNC of rigging the 2016 primary against Sanders.

"The Crooked DNC is working overtime to take the Democrat Nomination away from Bernie, AGAIN!" Trump wrote on Twitter in February, when Sanders was still in the race. "Watch what happens to the Super Delegates in Round Two. A Rigged Convention!"

Sanders supporters even unsuccessfully sued the DNC in 2017, alleging the Democratic Party's coordination with the Clinton campaign against the Vermont senator amounted to election fraud.

Now, Sanders is playing nice with Democratic leadership by supporting Biden as the 2020 election approaches.

2. He's an independent in the Senate

Sanders' official party affiliation in the Senate is as an independent, though he caucuses with the Democrats. The self-declared democratic socialist is one of the most liberal members of Congress, at times bucking Democratic leadership when it works with Republicans on moderate legislation.

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"I am an independent and I have always run in Vermont as an independent, while I caucus with the Democrats in the United States Senate. That's what I've been doing for a long time and that's what I’ll continue to do,” Sanders said in the interview as he announced his 2018 reelection campaign to the Senate.

Sanders with his wife Jane, speaks during a campaign event in San Antonio, Saturday, Feb. 22, 2020. (AP Photo/Eric Gay)

Sanders does, however, have good relationships with many Democrats and a lot of supporters in the Democratic base, which is a good thing for him as it's almost impossible to win a national election while representing a third party.

3. He's released a folk album

Sanders, who was the mayor of Burlington, Vt., before making his way into the House of Representatives and eventually the Senate, in 1987 released a political folk album with the help of a producer and a group of Vermont musicians.

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Its tracks include "We Shall Overcome," "This Land is Your Land" and "Oh Freedom."

4. He had a heart attack in 2019

Sanders suffered a heart attack in October, as the presidential campaign was well underway. He seemed to recover quickly, however, and was back on the debate stage later that month.

Sanders released his medical records in December, which included a note from his doctor that said, "You are in good health currently and you have been engaging vigorously in the rigors of your campaign, travel and other scheduled activities without any limitation."

Biden speaks as Sanders listens during a Democratic presidential primary debate, Nov. 20, 2019, in Atlanta. (AP Photo/John Bazemore)

5. The 78-year-old is endorsed by some of the youngest members of Congress

At 78 years old, Sanders is older than fellow septuagenarian presidential candidates Trump, Sen. Elizabeth Warren, D-Mass., and former New York City Mayor Michael Bloomberg. But Sanders has snagged endorsements from 75 percent of the "Squad," a high-profile group of young, freshman congresswomen who are part of a larger effort to drag the Democratic party to the left.

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Reps. Alexandria Ocasio-Cortez, D-N.Y., Rashida Tlaib, D-Mich., and Ilhan Omar, D-Minn have all endorsed Sanders' campaign for president. Fellow 'Squad' member Rep. Ayanna Pressley, D-Mass., endorsed Warren, her home-state senator.

FOX News' Tyler Olson and Jennifer G. Hickey contributed to this report.