Once again, it's economic anxiety
https://www.nytimes.com/2017/08/24/opinion/donald-trump-identity-politics.html
Donald Trumps Identity Politics
Thomas B. Edsall | AUG. 24, 2017
...
Between Jan. 22 and Jan. 28, 2016, as Trump consolidated his early support on the eve of the Republican caucuses and primaries, ANES conducted a special pre-election survey. To explore the role of white voters for whom racial identity was especially important, three political scientists John Sides, Michael Tesler and Lynn Vavreck analyze the ANES data in their forthcoming book, Identity Crisis: The 2016 Presidential Campaign and the Battle for the Meaning of America.
The survey, they write,
asked four questions that captured dimensions of white identity: the importance of white identity, how much whites are being discriminated against, the likelihood that whites are losing jobs to nonwhites, and the importance of whites working together to change laws unfair to whites. We combined those questions into a scale capturing the strength of white identity and found that it was strongly related to Republicans support for Donald Trump.
On the basis of that scale, the authors assembled the data illustrated by the accompanying chart, which shows that fewer than five percent of white Republicans who indicated that their racial identity was of little importance supported Trump. Among those who said their identity as whites was extremely important to them, Trumps support reached 81 percent.