From The New York Times, The End of Identity Liberalism by Mark Lilla
But the fixation on diversity in our schools and in the press has produced a generation of liberals and progressives narcissistically unaware of conditions outside their self-defined groups, and indifferent to the task of reaching out to Americans in every walk of life. At a very young age our children are being encouraged to talk about their individual identities, even before they have them. By the time they reach college many assume that diversity discourse exhausts political discourse, and have shockingly little to say about such perennial questions as class, war, the economy and the common good. In large part this is because of high school history curriculums, which anachronistically project the identity politics of today back onto the past, creating a distorted picture of the major forces and individuals that shaped our country. (The achievements of women’s rights movements, for instance, were real and important, but you cannot understand them if you do not first understand the founding fathers’ achievement in establishing a system of government based on the guarantee of rights.)
But it is at the level of electoral politics that identity liberalism has failed most spectacularly, as we have just seen. National politics in healthy periods is not about “difference,” it is about commonality. And it will be dominated by whoever best captures Americans’ imaginations about our shared destiny. Ronald Reagan did that very skillfully, whatever one may think of his vision. So did Bill Clinton, who took a page from Reagan’s playbook. He seized the Democratic Party away from its identity-conscious wing, concentrated his energies on domestic programs that would benefit everyone (like national health insurance) and defined America’s role in the post-1989 world. By remaining in office for two terms, he was then able to accomplish much for different groups in the Democratic coalition. Identity politics, by contrast, is largely expressive, not persuasive. Which is why it never wins elections — but can lose them.
The Democratic party has cried wolf so often on race that no one listens to them anymore. Without it their policies have little appeal, and their failures become more apparent.
Emotional appeal still works in politics. But negative emotions are also strong. Their appeal to the SJW crowd has less clout because of the success won in the last generation. But the negative emotion of contempt drove many a voter to the possibility of Trump, even if it was a reluctant move.