Trump's presidency is over. So are many relationships.

The people I interviewed generally thought that if Trump had never entered politics, their relationships wouldn’t have deteriorated as they did. They may be correct, but this obscures a longer-running trend that seems to be fueling relationship-ending political disputes.

As political scientists have documented, over the past few decades, Americans’ party affiliations have become more strongly correlated with other aspects of who they are, such as their race, their religion, and where they live. As a result, certain political beliefs have become more predictably linked to broader worldviews. “Politics isn’t just politics anymore,” Emily Van Duyn, a communication professor at the University of Illinois, told me. “Political identity now encompasses so many other things—our social identity, our morals, our values.” This means that when two people disagree about a political figure, much more than a preference in candidates and their policies is often at stake.

While Trump didn’t create this dynamic, he did exacerbate it by constantly stoking political animosity and cultural division. Van Duyn, who has studied political disagreements in romantic relationships, said, “I think his bombastic approach to social mores in many ways forced people to have a reckoning around, Oh, my spouse supports Trump—what else does that encapsulate now? If he supports Trump, does he also hate me as a woman?”