A 2016 Gallup poll on affirmative action was typical in finding majorities of all groups (76 percent of whites) who believed that merit alone should determine college admissions, with race or ethnicity playing a relatively minor role. Nevertheless, just last year, a closely divided Supreme Court affirmed an earlier decision that narrow use of race may be one of the many factors in undergraduate admissions at the University of Texas.

There is good reason to suspect that universities may not follow the letter of the law. Data from the Association of American Medical Colleges indicate that race is a substantial factor in medical school admissions, not one of many. For example, from 2013 to 2016, medical schools in the United States accepted 94 percent of blacks, 83 percent of Hispanics, 63 percent of whites and 58 percent of Asians with top MCAT scores of 30 to 32 and grade-point averages of 3.6 to 3.8; for MCAT scores of 27 to 29 (G.P.A. of 3.4 to 3.6), the corresponding figures are 81 percent, 60 percent, 29 percent and 21 percent. For low-range MCAT scores of 24-26 (G.P.A. of 3.2 to 3.4), 57 percent of blacks were admitted, 31 percent of Hispanics, 8 percent of whites and 6 percent of Asians.

The presidential candidates in 2016 were largely silent on affirmative action, but Mr. Trump said in 2015 that he was “fine with it” though “it’s coming to a time when maybe we don’t need it.” Affirmative action and new diversity dictates were most likely an “unspoken but heard” issue.

Institutional racism remains a problem, as does immigration and the balancing of assimilation and pluralism. But identity politics and identity policies may have become too divisive and complicated in both theory and practice.

Since the election, many Democrats have been talking less about diversity and more about unifying cultural and economic commonalities. The new Democratic “Better Deal” populist blueprint put forward by Senator Charles Schumer of New York echoes his admiration for the New Deal by emphasizing strategies that would help all American workers.

Mr. Schumer knows his party must quickly and candidly address the question of why the white working and middle classes — groups who were the foundation of Franklin Roosevelt’s New Deal coalition — often support Mr. Trump.