(Ashlee Rezin/Sun-Times Media via AP )

One day ahead of Illinois's all-important Democratic presidential primary, embattled Chicago Mayor Rahm Emanuel (D) is probably wishing it were over already.

Over the weekend, Sen. Bernie Sanders (I-Vt.) made Emanuel Public Enemy No. 1 as Sanders campaigns hard to win the state, which is the second-biggest delegate prize among the five states voting in Democratic contests Tuesday. Sanders-approved ads are up on Chicago airwaves with local officials blasting the mayor, who is a Hillary Clinton supporter and who faces continued unrest in his city over his administration's handling of the police shooting of Laquan McDonald.

Witness this brutal ad:

And Sanders is repeating lines like this in speeches and press conferences:

Clinton, meanwhile, isn't exactly bear-hugging the mayor. On Monday, Bloomberg reported that the Democratic front-runner won't meet with Emanuel when she's in Chicago on Monday. The mayor's office told Bloomberg their schedules don't line up. Bloomberg noted that Clinton's campaign is regularly in contact with Emanuel, and Bill Clinton spent time with the mayor last week.

But the political significance of Emanuel and Clinton being unable to find time to huddle together a day before the state's presidential primary is hard to miss. Emanuel is a longtime Clinton ally and a former top official for her husband. He was one of Clinton's first supporters when she was considering a second presidential run. And their missed greeting comes right as Sanders aims directly at their relationship in his bid to win Illinois, which some polls show is a toss-up.

Clinton's public comments about Emanuel have trended from supportive -- saying in December that she was "confident" in the mayor -- to more skeptical. Here's what she said in mid-January on "Meet the Press."

When pressed specifically on Emanuel, she said, "Mayor Emanuel has said that he is committed to complete and total reform and I think he should be held to that standard," adding that it's "going to be up to him and up to the people of Chicago" to prove his credibility.

The suggestion here is that Emanuel might be too toxic for Clinton -- and perhaps everyone else who's avoiding his handshake or endorsement. A poll last month showed just 27 percent of Chicagoans approve of his job performance, and four in 10 want him to resign. Support for his resignation was higher with black voters, who have been so key to Clinton's success so far in the Democratic presidential primary and will be again on Tuesday.

Of course, at this point, Emanuel is no stranger to snubs. A Twitter user over the weekend resurfaced a months-old NBC 5 Chicago clip of Emanuel trying to shake hands with someone during a public budget meeting turned hostile; the guy wasn't having it.

His police department is facing a federal civil rights investigation into the 2014 police-involved shooting of 17-year-old McDonald and alleged cover-up. He's also dealing with a long-simmering, contentious battle with Chicago's teachers over budget woes. Emanuel is facing calls to resign from several prominent black city leaders and the Chicago Teacher's Union, as well as pending legislation to create a system to recall him. (Even though Emanuel's friend, Republican Gov. Bruce Rauner, recently said he'd approve such legislation, it will be politically difficult to get through the Democratic-controlled legislature.)

There are racial overtones to the presidential drama swirling around Emanuel that could explain why he's in the spotlight for all the wrong reasons right now. Broadly speaking, Sanders has struggled with black voters, while Clinton has done well. (That was less the case in Michigan last week than in the many Southern states Clinton has won, but she still won black voters more than 2-to-1.) Sanders's sudden pivot to Emanuel is clearly aimed at chipping away at what is perhaps his campaign's biggest weakness.

Taken together, Emanuel's recent controversies, the dynamics of the Democratic presidential race and his profile as a national figure mean that this week, Emanuel is one of politics' biggest punching bags.