In surveys by the nonpartisan Public Religion Research Institute, Americans who support Trump were far more likely than those who don’t to say that police shootings of black men are only isolated incidents and to claim that discrimination against whites is now as great a problem as bias against minorities.

Politically, the heightened focus on police behavior and racial inequities more broadly could compel Trump to squeeze out bigger margins and turnout from the white constituencies most skeptical that racism remains a widespread problem, in order to offset what could be a further decline in November among the groups in all races that do consider bias an enduring blight on American life.

Over the next 30 years, the share of Americans who said blacks had equal opportunities with whites drifted slightly higher in Gallup polling, reaching nearly four-fifths overall (and slightly above four-fifths among whites) in 2009 after Barack Obama’s election as the first African American president.

It found the share of whites who said that discrimination primarily explained the economic gaps between whites and blacks fell from around two-fifths during the late 1970s to 32% or less from 2006 to 2014, according to results provided by Tom W. Smith, who directs the General Social Survey.

But beginning in Obama’s second term and continuing under Trump, polling by Gallup, the NORC and the Pew Research Center all shows a general uptick in concern about racial discrimination.