helpful research on "evangelical Christianity" vs. "supporters of" vs. "voted for" Trump

This work-- the op-ed version and the longer/better version-- is relatively good (and a big improvement over the usual nada) at measuring "support" for Trump-- by looking at primary voting (when GOP voters and many evangelicals had more choices) rather than voting in November (when the choices were limited and historically unenviable). 

Ideally, such studies would go further-- beyond mere attendance to other forms of religious practice or belief. But this is certainly an improvement on the common practice of lumping self-styled evangelicals into one basket.