Wisconsin Democratic Sen. Tammy Baldwin and Vermont Sen. Bernie Sanders have come under fire for sharing a stage with a progressive activist who is a 9/11 conspiracy theorist.

Sanders appeared alongside Baldwin and other Democrats Monday at the University of Wisconsin-Milwaukee, urging people to vote for Democrats in the upcoming November midterm election and support Baldwin’s re-election against Republican Leah Vukmir.

But before Baldwin and Sanders took the stage, a Chicago-based progressive activist and hip-hop artist known as Solo Littlejohn warmed up the crowd.

He introduced himself as a “leader of Fight For 15,” a Sanders-backed group campaigning for a $15 minimum wage and trade unions, and went on to praise the progressive politicians for supporting his cause.

The group also shared Littlejohn’s speech at the rally on its Twitter page.

But Littlejohn’s social media reviewed by Fox News reveal that he shared a conspiracy theory that the September 11, 2001 terror attacks were staged, suggesting that the buildings were destroyed by controlled demolition.

The Myspace post from 2009 also includes a link to InfoWars.

He also listed his “influences” on Myspace, including Cuban revolutionary leader Ernesto Che Guevara, Black Panthers’ co-founder Huey P. Newton, and “all real revolutionaries.”

Vukmir’s campaign slammed the Democrat for campaigning with the conspiracy theorist.

“Senator Baldwin — who supported impeaching President Bush, voted against the resolution in honor of the 9/11 victims and sided with the 9/11 mastermind against CIA administrator Gina Haspel — is now campaigning with a 9/11 conspiracy theorist,” Jess Ward, the campaign manager, said in a statement.

“Wisconsinites deserve a senator who will protect America when we are attacked, not side with our enemies.”

"Senator Baldwin — who supported impeaching President Bush, voted against the resolution in honor of the 9/11 victims and sided with the 9/11 mastermind against CIA administrator Gina Haspel — is now campaigning with a 9/11 conspiracy theorist." — Jess Ward, the Vukmir campaign manager

Baldwin and Sanders’ campaigns did not respond to Fox News requests for a comment. Littlejohn didn’t respond to a request for an interview.

The progressive activist also made other troubling comments on other social media sites, including numerous explicit messages on Twitter.

In one of his tweets, he wrote: “Ronald Reagan When I Send A Contra-Band Of [explicit] To Shoot Up Your Kids, While They Rape your Baby's Mama N----!”

More recently on Facebook, he joked about drug usage and shared pictures showing large quantities of drugs. Littlejohn himself was sentenced in 2006 at least three months in jail for marijuana possession, according to legal documents obtained by Fox News.

He also floated a debunked conspiracy theory that the U.S. government was found guilty in the murder of Martin Luther King.

Littlejohn expressed anti-police sentiments multiple times and once shared a picture suggesting police academies train future officers how to murder someone without consequences.

He became increasingly political amid the 2016 presidential election, sharing a number of anti-Trump posts. In one of the posts on Facebook, he compared Trump to Nazi Germany leader Adolf Hitler and captioned with “#SameTactics” hashtag.

Baldwin is currently leading Vukmir by nearly 10 points, according to a recent poll, though the lead has decreased in recent months.