In “Vote Switching in the 2016 Election,” a paper published in the spring of 2019, Tyler T. Reny, Loren Collingwood and Ali A. Valenzuela, political scientists at U.C.L.A., UC-Irvine and Princeton, argue that before Trump

the white working class has felt increasingly alienated from both parties, neither of which look like their group or are perceived as representing their group’s interests.

White voters, they contend,

are increasingly perceiving the Democratic Party as the party of racial and ethnic minorities and racially liberal policy and the Republican Party as the party of White Americans and racially conservative policy.

The three authors argue that “significant changes in voting across party lines, particularly for the presidency, precede changes in party identities, the basis for realignments.”

In their March 2018, paper, “Hunting where the ducks are: activating support for Donald Trump in the 2016 Republican primary,” Sides, Tesler and Vavreck make an important observation:

As Republican Party leaders and elites dealt with the nomination of Donald J. Trump, they often looked inward — blaming themselves for failing to change the beliefs of Republican voters that helped propel Trump, or at least for failing to handle key issues in a way that might defuse Republican voters’ concerns.

Sides and his co-authors quote an operative for the Koch Brothers’ network of conservative voter mobilization groups, a network that did not anticipate or support Trump:

We are partly responsible. We invested a lot in training and arming a grass roots army that was not controllable, and some of these people have used it in ways that are not consistent with our principles, with our goal of advancing a free society, and instead they have furthered the alt-right.

What Republican leaders did not appear to understand, the authors concluded,

was just how longstanding and potent this constellation of sentiments was. Trump successfully activated beliefs, ideas, and anxieties that were already present and even well-established within the party. He simply hunted where the ducks are in the Republican Party.

Trump’s genius in 2016 lay in his willingness — indeed, his eagerness — to openly and aggressively unleash the forces of racial and ethnic hostility that Republican elites had quietly capitalized upon for decades. Trump will be a formidable candidate next year because he is prepared to look under the rocks of the American belief system and see the snakes and vermin that have camped there in the dark.

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