Khizr Khan, whose son, Humayun S.M. Khan, was one of 14 Muslim Americans who died serving in the U.S. Army in the 10 years after the Sept. 11, 2001, terrorist attacks, offers to loan his copy of the U.S. Constitution to Republican  presidential nominee (now president) Donald Trump as he speaks  during the last night of the Democratic National Convention in Philadelphia on July 28, 2016. (Mike Segar/Reuters)

Last Wednesday, the Pew Research Center released the results of a new survey showing that American attitudes toward Muslims had improved in the past few years. While respondents to a 2014 survey gave Muslims an average rating of 40 on a 100-point “feeling thermometer” — a scale measuring favorability toward different groups — that number had climbed to 48 by last month. Headlines noted the shift, which many observers found surprising given recent debates about terrorism and President Trump’s order banning immigrants from seven Muslim-majority nations.

[How Trump changed Americans’ view of Islam – for the better]

But despite the improved attitudes, Muslims remain the least popular of all religious groups asked about in the Pew survey. By comparison, respondents gave Jews a rating of 67, Catholics 66, and mainline Protestants 65. Even atheists were rated higher at 50.

Data in the figure below from the 2016 pilot study of the American National Election Studies (ANES) show the same thing. On a feeling thermometer, Muslims are ranked near the bottom compared with other groups in the United States — including blacks, Latinos, transgender people and gays and lesbians — and below the neutral point of 50.

What explains this deep prejudice toward Muslims?