There were a few surprises for me in this summary of a March working paper by Larry Bartels:

…we look at the underlying ideological and partisan sentiments of Republican and Democratic voters. Prof. Larry Bartels of Vanderbilt University did just that in a revealing working paper titled “Partisanship in the Trump Era,” released last month. In it, Bartels closely examined a November 2017 YouGov survey of 2,000 people, all of whom were originally interviewed in 2015 and 2016 as part of YouGov’s 2016 Cooperative Campaign Analysis Project. After putting all three of those survey findings through rigorous regression analyses, a great deal of conventional wisdom about what’s going on in the Republican Party was blown to bits.

https://niskanencenter.org/blog/political-landscape-not-even-close-think/