On Wednesday, Hillary Clinton is giving a speech focused in part on Americans with disabilities, and the need to help all of them. It’s a rather warm-and-fuzzy topic for such an acrimonious campaign, but the story of how speaking up for the disabled came to represent a polarized issue is a microcosm of how even once-universally supported positions have become partisan fodder.

Clinton’s speech Wednesday is part of a push for positive stories by her campaign, as a way of countering a string of negative stories as well as her high unfavorables. Her campaign previewed the speech in Orlando, saying the Democratic nominee would “​​make the case for building an inclusive economy that welcomes people with disabilities, values their work, rewards them fairly, and treats them with respect.” She’s also touting her own plans to help people with disabilities, including banning subminimum wages and working with businesses to encourage and incentivize hiring of people with disabilities.

At a rally in Greensboro, North Carolina, last week, Clinton was introduced by Martha Soltani, whose daughter Sara was born deaf but was aided by the Children’s Health Insurance Program, which Clinton helped push into law in the 1990s.

You’d think none of that would be all that controversial. Disabilities strike across age groups, racial barriers, and partisan lines. In this election, even this is a polarized issue—though the roots of that split actually date back to before Donald Trump was a major political figure.

Disability politics used to be bipartisan. The Americans with Disabilities Act was primarily authored by Senator Tom Harkin, an Iowa Democrat. It passed the Senate and House overwhelmingly—91-6 and 377–28, respectively, and was signed into law by President George H.W. Bush in 1990. When he signed the law, Bush said:

Now I sign legislation which takes a sledgehammer to another wall, one which has for too many generations separated Americans with disabilities from the freedom they could glimpse, but not grasp. Once again, we rejoice as this barrier falls for claiming together we will not accept, we will not excuse, we will not tolerate discrimination in America…. To those Members of the House of Representatives with us here today, Democrats and Republicans as well, I salute you. And on your behalf, as well as the behalf of this entire country, I now lift my pen to sign this Americans with Disabilities Act and say: Let the shameful wall of exclusion finally come tumbling down.

Eighteen years later, Bush’s son George W. Bush signed some expansions of the ADA into law.

Since then, however, things have sputtered. In 2012, the Senate failed to ratify a United Nations treaty called the Convention on the Rights of Persons With Disabilities. Democrats supported the treaty, but Republicans were split. On the pro side were George H.W. Bush and Bob Dole, the former Senate GOP leader and presidential candidate who was injured during World War II. On the con side were a bloc who warned on extremely dubious grounds that the treaty would allow the UN to meddle in U.S. courts. In the end, the treaty failed, despite Dole himself appearing on the Senate floor to lobby. It needed two-thirds of votes to pass, but was only able to garner 61.

The Trump campaign has only exacerbated any such splits. The most egregious moment came when he mocked New York Times reporter Serge Kovaleski. Trump falsely claimed he’d seen Muslims celebrating 9/11 in the streets in New Jersey, and pointed to reporting Kovaleski, who was then a reporter for The Washington Post. When Kovaleski, who has a congenital condition affecting his joints, contradicted Trump, Trump mocked him, doing a physical impression of Kovaleski:

Trump denied that he was mocking Kovaleski, despite the evidence. He also argued that his legally required compliance with the ADA proved his support for the disabled, although as Gideon Resnick pointed out, Trump has been sued repeatedly for violating the ADA. He also appeared to mock conservative pundit Charles Krauthammer, who is paralyzed from the waist down, saying, “I get called by a guy that can't buy a pair of pants, I get called names? Gimme a break.”

As Irin Carmon reported, disability advocates were displeased by Trump’s decision to name his campaign book Crippled America. In a 2011 book, meanwhile, he wrote, “Then there's the disability racket. Did you know that one out of every 20 people in America now claims disability? That adds up to $170 billion a year in disability checks. Between 2005 and 2009, it is estimated that $25 billion were eaten up in fraudulent Social Security Disability Insurance filings. On and on, scam after scam it goes; as always, taxpayers are the ones getting stiffed.” (The idea that disability insurance is being overused is one sometimes voiced by analysts across the ideological spectrum.)

All of this makes Trump an alluring target for the Clinton campaign. An August Bloomberg poll, for instance, found Trump’s mockery of Kovaleski to be the single most disliked moment of his campaign. In June, PrioritiesUSA, a super PAC supporting Clinton, launched a brutal ad spotlighting the comments:

That was not uncontroversial on its own. As David M. Perry wrote in The Atlantic, “It’s exciting to see disability issues play a role in the campaign, and gratifying to see a politician take heat for humor that offended many people. The ad, however, also plays into stereotypes about disability, revealing tensions between disability-rights activists and mainstream politicians.”

But Clinton’s focus on disability issues isn’t just a matter of electoral jockeying. It’s also in line with the direction of progressive politics as a whole. The Democratic Party has increasingly embraced the language and agenda of social justice. As my colleague Clare Foran noted back in March, Clinton herself has adopted the language of intersectionality, the idea that forms of discrimination, marginalization, and inequality should not be considered singly but as a complex, with different forms compounding one another.

This shift is not without a reaction. The Trump campaign has seized on “political correctness” as a great ill afflicting America. White, straight, male voters who lean toward Trump, and who are those least affected by discrimination, might be inclined to dismiss discussions of intersectionality as simply more political correctness. The two moves in concert produce a feedback loop: Progressives become more and more concerned about the dismissal of intersectional concerns, while that growing concern only convinces conservatives that the attention being paid to matters of race, disability, class, or gender are disproportionate and a result of political correctness.

In other words, the 2016 presidential campaign may have produced a sharpened and accelerated partisans split on disability accommodation, transforming them from a universal concern to a wedge issue, but November 8 is unlikely to mark the end of the trend or any renewed unity.