At this week's debate, Donald Trump doubled down on a claim about his canceled rally at UIC Pavilion in March: the idea that the protesters at his rally were paid to do so.

I was wondering what happened with my rally in Chicago and other rallies where we had such violence. [Hillary Clinton's] the one and Obama that caused the violence. They hired people—they paid them $1,500, and they’re on tape saying be violent, cause fights, do bad things.

It's a claim he's repeated a few times, though his campaign is unable to provide any proof, according to nonpartisan fact-checking website PolitiFact. Trump refers to a video by discredited filmmaker James O'Keefe, who is known for deceptive editing and unethical tactics. Though the video has been embarrassing for Democrats, the recorded conversations don't prove Trump's claims; for one, they took place after the Chicago rally.

Those watching in Chicago, many of whom attended the rally, were incredulous; some started tweeting at Trump, jokingly asking where they could pick up their $1,500 checks.

Why is Trump so fixated on discrediting Chicago protesters? Trump's been known to ignore or deny evidence that he's not as well liked as he thinks—for instance, citing favorable-but-unscientific polls while ignoring more accurate ones that suggest he lost the debates. But perhaps another clue lies in the composition of protesters at that rally, where anti-Trump forces galvanized themselves in an unprecedented way that the GOP nominee likely has trouble grasping.

They were diverse. They were organized. And they were powerful.

Trump and the GOP establishment have struggled mightily to stitch together a coalition of more than just non-college-educated male whites. (As my colleague Whet Moser reported, the party of Lincoln is projected to get as little as 1 percent of the black vote in some states.) And the campaign itself is notoriously disorganized. His top campaign staff has gone through a revolving door, his national political director has “take[n] a step back” from the campaign, and just last week Trump himself mistakenly told his supporters to vote on November 28.

Meanwhile, reports and photographs from that March rally show a vast array of groups who turned out to oppose Trump, including Latino and immigration rights groups, Black Lives Matter and affiliated African American groups, Muslim and Arab American groups, Hillary supporters, Bernie supporters, UIC's Greek Council, union groups—basically, a wide cross-section of Chicago. And our protest community (especially Black Lives Matter groups) is highly organized and strategic. The Trump mega-protest was just another example of how these groups know how to build coalitions and show solidarity.

The Trump campaign's inability to understand what happened in Chicago became baldly clear when former campaign manager Corey Lewandowski told CNN in August:

"That is a black community. He went to the heart of Chicago to go and give a speech to the University of Chicago in a campus, which is predominantly African American, to make that argument," Lewandowski said, mistaking the name of the university where the speech was supposed to take place. "And you know what happened? The campus was overrun and it was not a safe environment."

For the record, UIC's black student population from 2010-2014 has hovered around 8 percent. And the Census tract where UIC Pavilion is located is about 51 percent white and 9 percent African American, according to 2014 data.

That says a lot about the campaign: It goes into a place that's 9 percent black and considers it "overrun" and "not safe." (Welcome to Chicago, Mr. Trump: the city is actually one-third black and one-third Latino, so you in fact stumbled into one of the whiter parts of town.) That doesn't differ too much from Trump's own assertions that all black people are slumming it in the inner cities, with "nothing to lose."

It all reminds me of a Matt Yglesias column this week. Trump supporters claim they are the "silent majority," trying to evoke the Nixon-era term. But the truth, Yglesias says, is the phrase applies far better to Hillary's supporters:

Data from the Pew Research Center shows that Republicans enjoy the allegiance of the vast majority of white voters without a college degree—a trend that Trump will, if anything, accelerate. Democrats, meanwhile, enjoy overwhelming majorities among people of color, who now comprise almost 40 percent of their party—a trend that Trump will, again, accelerate. White Democrats these days are mostly college graduates, and mostly women. And while white male Democrats will back Clinton over Trump, they went pretty overwhelmingly for Sanders in the primaries. Clinton’s core coalition is composed of racial minorities and well-educated women, especially unmarried ones. Clinton also enjoys the support of more than 70 percent of LGBTQ Americans and is trouncing Trump with Jewish voters by higher margins than any 21st-century Democrat.

Emphasis mine. As Yglesias points out, women and racial minorities don't necessarily have a ton in common. It'd be a huge mistake to think of them as one homogenous bloc. But the Democrats, and Clinton's campaign in particular, has worked hard to give everyone a reason to get on board. There have been ads in important markets appealing to certain groups; there have been celebrity endorsements strategically sprinkled among nerds, pop lovers, and Kimye apologists alike. Not only has Clinton explicitly said that diversity is a strength of the nation, Clinton's campaign has expertly directed its messaging at diverse groups, thus building a coalition that now gives her a 93 percent chance of winning the election.

To Trump, Chicago's raucous protest crowd may have looked too organized, too diverse to be real. But the truth is, this is an accurate picture of Chicago—and more and more, the whole of America. And for Republicans, that could be a problem, not just for Trump in 2016, but for the entire party in years to come.