"What impresses me is how Joe Biden has turned his pain into empathy and service," Lightfoot said. "I know he is a fighter."

Lightfoot’s endorsement, which she first teased to civic leaders and members of the First Friday Club of Chicago behind closed doors, comes just a day before Bernie Sanders is scheduled to swoop into the city for a rally at Grant Park — the same place Barack Obama held his 2008 victory speech.

The mayor leads the nation's third-largest city and hasn’t always been on board with Biden. In an interview with POLITICO last year, Lightfoot said the former vice president needed to atone for how Anita Hill was treated when she testified before Congress during Clarence Thomas’ Supreme Court confirmation hearings nearly three decades ago. Biden, a senator at the time, chaired the hearings.

“I don’t think Anita Hill needs his apology. But give an account of your behavior with a lot of hindsight,” Lightfoot said at the time, recalling how she was riveted by the 1991 hearings after recently graduating from law school. “I don’t know that he’s successfully done that yet.”

But now Lightfoot joins a long list of African American elected officials in Chicago moving into the Biden camp, including Reps. Danny Davis and Robin Kelly.

The mayor said she and Biden talked by phone and when asked whether they addressed Anita Hill, Lightfoot said, “Let’s just say we had a very good conversation.”

Still, Sanders has a bench of supporters in Illinois among Latino politicians, such as Rep. Jesus “Chuy” Garcia (D-Ill.). Jill Biden was in Glencoe, Ill., a suburb north of Chicago, Friday for a fundraiser that made about $100,000, according a campaign pool report.

Rep. Bobby Rush hasn’t announced who he’s backing since his candidate, Mike Bloomberg, exited the race. And freshman Democratic Rep. Lauren Underwood, whose swing district supported Donald Trump in 2016, has said she would stay neutral.

Lightfoot has made it clear that she didn’t align with Sanders on key issues, and expressed concern about how his campaign treats women, particularly after reports of Hillary Clinton saying his 2016 campaign was rife with sexism.

The mayor also rejected Sanders’ democratic socialism message.

Still, Lightfoot recently hinted she wouldn’t endorse Biden or Elizabeth Warren, either. Like Sanders, Warren also backed a strike put on by the Chicago Teachers Union last year, putting them at odds with Lightfoot. Biden hadn't contacted her for much of the campaign to discuss his candidacy, despite visiting Chicago several times.

The slights created speculation she’d eventually endorse Bloomberg, whom she had met with a few times during his visits to Chicago.

Ultimately, Lightfoot was always expected to support whoever the Democratic nominee is, as she’s been adamant in her opposition to Trump, even turning down meetings in the White House with fellow mayors and the president.