Back in December, Jeb Bush christened Donald Trump the “chaos candidate.” Those words took on a new meaning on Friday night, when he was forced to cancel a rally at the University of Illinois at Chicago after protesters overwhelmed the event and fights broke out. “It became a Bernie Sanders rally,” Jedidiah Brown, who rushed the podium and ripped apart a Trump sign, later told MSNBC. 

Reporters from The Guardian described the scene: 

Fights and scuffles broke out as protesters swapped blows with Trump supporters and activists eager to celebrate their apparent victory shouted “Bernie, Bernie” and “Si se puede” (“Yes we can”), while waving signs supporting the Democratic candidate Bernie Sanders.

It is impossible to determine what percentage of these protesters—a loose coalition of UIC students and experienced activists from Black Lives Matter, the Black Youth Project,, Fight for 15, and the Chicago Teacher’s Union—will turn out to vote for Sanders in the Illinois primary on Tuesday. Still, it is remarkable that within a year, some Black Lives Matter activists have gone from shutting down Sanders at his own events to chanting his name at a Trump rally.

Illinois will be a huge test for Sanders and for Hillary Clinton. FiveThirtyEight gives the former secretary of state a 95 percent chance of winning, but then again, the site gave her a 99 percent chance of winning Michigan, which she lost in a squeaker. As Harry Enten wrote after Sanders made him “eat a stack of humble pie” in Michigan, “The question I am asking myself now is whether this means the polls are off in other Midwestern states that are holding open primaries.”

Sanders certainly hopes so, as he has pushed an anti-free trade message that has resonated in the Rust Belt. But his campaign, which outperformed expectations among black voters in Michigan, has also rolled out ads tailored to voters in Chicago, where Clinton has deep roots and support from the “Democratic machine.” In one, outspoken Chicago Public Schools principal Troy LaRaviere says, “In Chicago we have endured a corrupt political system and the chief politician standing in the way of us getting good schools is our mayor.” Without saying her name, he ties Clinton to Mayor Rahm Emanuel. Sanders, meanwhile, has become a strong critic of Emanuel.

The day after Trump’s rally at UIC, Sanders held a press conference in Chicago. He was introduced by LaRaviere and Asean Johnson, a middle schooler who captivated Chicagoans in 2013 after delivering a passionate speech against the mayor’s decision to close more than 50 public schools. Joining them was Cook County Commissioner Chuy García, a Sanders surrogate who forced Emanuel into the first mayoral runoff in Chicago history last year (Emanuel defeated him 56 to 44 percent, thanks largely to wealthy white voters). Clinton, meanwhile, was in Chicago on Monday, but didn’t meet with Emanuel. His spokesman assured Bloomberg that “the mayor’s support for President Clinton and Secretary Clinton is well known.”

Sanders is expected to do well among urban millennials and white voters downstate. He doesn’t need to outperform Clinton among black and Latino voters in Chicago, but if he can peel off enough support, he could pull a Michigan-style upset. That’s why he’s focusing on local issues affecting Chicago voters—public schools, a budget crisis, and a mayor that is viewed by many as callous and corrupt. A high turnout would likely favor Sanders, and Chicago voters are expected to be motivated by the city’s handling of the Laquan McDonald case and by a contentious state’s attorney race, which will also be decided on Tuesday.