Republicans cross-pressured by partisan loyalty, on one hand, and aversion to Trump on the other, Kane added, “may instead opt to abstain from voting at all.”

In the calculus of elections, an abstention from voting amounts to a gain of one vote, while a conversion — from Republican to Democrat or vice versa — amounts to two: one lost by the other side and one gained for yours.

Julie Wronski, a political scientist at the University of Mississippi, who wrote the “Ingroup Lovers or Outgroup Haters?” paper with Kane and Lilliana Mason of the University of Maryland, noted in an email that

in all of our statistical models, the effect of voters’ party ID was larger than the effect of their group feelings. So while warmth toward groups like blacks and Muslims can make voters amenable to Democratic candidates, it’s unclear whether these feelings can override the strong and longstanding influence of partisanship.

Wronski pointed out in an email that Trump is campaigning

largely on issues of white identity. And given the exchange Thursday night between Joe Biden and Kamala Harris on school busing, it appears the Democratic Party is going to also focus on identity-based issues in 2020. Thus, it is looking like feelings toward the groups targeted by the candidates will matter.

All of which helps explain Trump’s shift to rolling back gay and lesbian rights, for example, after many decades of supporting just those causes.

In the midst of the 2016 presidential campaign, Trump described himself as a “real friend” of the LGBTQ community. Since taking office, however, the Trump administration has argued that the 1964 Civil Rights Act rights law does not protect gay workers from discrimination and that transgender people should be barred from military service.

There is an underlying political logic to the switch from Trump’s campaign stance to his policies once he won the White House. As he heads into the 2020 election, his “base,” the voters essential to his re-election, are hostile not only to gay men and lesbians, but to racial and ethnic minorities as well.