I recently read the book, The End of White Christian America by Robert Jones. He's the CEO of PRRI, a institution in Washington that researches public attitudes toward religion. The book traces the history of political involvement in politics by White Christians and their institutions. He covers the Mainline and Evangelical streams as two parts of the same whole. and sees the same demographic and political pressures facing them both; the two streams are following the same trajectory of waning numbers and influence, with the Mainline about 20 years ahead of evangelical Christianity in terms of timeline.
The two issues he traces in detail are gay marriage and race. He shows how White Christianity was on the wrong side of both of these issues, and that the attitude - and the laws - of the country have moved faster and farther than White Christianity wanted to go.
The mood of the book is valedictory, even eulogistic. It begins with an "obituary" for White Christian America, and the long last chapter is, in fact, called "A Eulogy for White Christian America." Basically, Jones' thesis is that the heyday of White Christianity - its agenda, and purporting to serve as the country's moral voice -- is over. If White Christianity is to have any influence going forward, Jones says. it will have to accept a seat at a much broader and more inclusive table, rather than expecting to sit at its head.
He traces the percentage of the voting population that identifies as Evangelical Christian over about the past 20 years, and finds that in every presidential election, that percentage has gone down. It rebounds a bit in the next mid-term (because older, whiter voters tend to vote more in mid-terms) but then it goes down even further in the next presidential year, and then up again (though lower than the time before) in the mid-terms.
The book was released last summer, so it was written before that, and there's no question that he expected the Democrats to win the presidential election. His book has the certainty about trends - even a sense of triumphalism - that only a person imputing political truths from statistical facts can generate. Reading it at the beginning of the Trump presidency is like reading a counter-factual.
So, what happened?
This question is partially answered, I think, in this article, by the National Review's Rich Lowry, from the Guardian: "Trump's New Culture War Has Left Liberals Reeling. They Thought They'd Won That Battle." It's worth reading the whole thing, but the basic point is that "Trump has reoriented and reinvigorated the culture war. He has wrenched it away from its decades-long focus on issues related to religion and sexual morality and created another axis around populism and nationalism."
These issues form a more secure basis around which to rally politically because they are at once more central to identity and less subject to policy developments or changes in the law. The media, governmental and business "elites" who once thought that their concerns (trade, for instance) were outside of and protected from the maelstrom over "culture" issue have now found their concerns just as vilified by Trump and his White base as any other "liberal" issues. (The right, including Trump, sees those forces as liberal; I see them as socially liberal but politically/economically the bastion of corporate neo-liberalism.)
Using immigration as an example: liberals thought the issue would have to be decided in its favor, because of "demographics" and the wishes of the business wing of the Republican Party that it be settled that way. The post-mortem of the Republican Party after the 2012 election said as much. But here we are, four years later, and the new president is worse than ever on immigration, and he has attracted to himself a core constituency that sees immigration as a signal issue, with both economic ("they're taking our jobs") and cultural (who gets to decide what an "American" is) valences.
Bringing these two pieces together: Jones, and the left in general, thought that the culture wars were a game of waiting out the death of conservative (or evangelical) White people. What we find instead is that White-identity politics is resilient and adaptive, and when the religious pieces were no longer effective, they could be replaced (or more accurately, expanded) by more nationalistic or secular pieces, with the result being even an expanded and reinvigorated base.
I don't have a policy or approach to suggest here; I'm more thinking through the issues. But from Marx on, leftists and liberals have expected that their (our) positions would come to pass by some natural progression of forces, and each time the recidivist right has proven them wrong. Trump and this resurgent White nationalism is no different. The arc of history may indeed bend toward justice, as Dr. King said, but it doesn't do so by itself. It has to be bent, by us, or it won't bend at all.