Even some prominent liberals like Robert Reich, the former Secretary of Labor under Bill Clinton, seem open to conspiracy theories of the sort typically espoused by figures like Alex Jones and Glenn Beck. (After the recent violent demonstration at the University of California at Berkeley, Mr. Reich raised the possibility that the far right “was in cahoots” with the agitators, writing a blog post titled “A Yiannopoulos, Bannon, Trump Plot to Control American Universities?”)

A simple explanation for this shift is that misperceptions often focus on the president and are most commonly held by members of the other party. Just as Republicans disproportionately endorsed prominent misperceptions during the Obama years (like the birther and death panel myths), Democrats are now the opposition partisans especially likely to fall victim to dubious claims about the Trump administration.

But the shift in vulnerability to conspiracy theories may have deeper psychological roots. Research suggests that people embrace conspiracy beliefs as a way to cope with perceived threats to control. In particular, Joseph E. Uscinski and Joseph M. Parent at the University of Miami have argued that conspiracy theory beliefs increase in response to group threats, including among losers of elections. These beliefs can help rally groups and coordinate action in response to a decline in status or power.

To evaluate this conjecture, the political scientists Christina Farhart, Joanne Miller and Kyle Saunders, who study conspiracy theory belief, compared how Democrats and Republicans changed in their responses to a conspiracy predispositions scale created by Mr. Uscinski and his co-authors.

The scale asks respondents to evaluate a series of statements:

Much of our lives are being controlled by plots hatched in secret places.

Even though we live in a democracy, a few people will always run things anyway.