Because mainstream culture frowns on irrational prejudice, race has become a central theme in campaigns for the White House.

The country seldom sees a week go by that President Donald Trump fails to scandalize the public with statements that sound racist and violate norms. Telling four minority women in Congress to go back where they came from simply crosses a line, given that all four are U.S. citizens and three were born here.

Clumsily associating illegal Mexican immigrants with rapists and murderers sounds racist, especially to Trump’s opponents who have no reason to extend him benefit of the doubt.

Trump proclaiming an American judge might treat him unfairly, because of the judge’s Mexican lineage, conveys ethnic bigotry.

We can go on with fair examples exuding presidential prejudice. Americans will dispute what he really means and how he really feels, basing opinions on their love or hatred of Trump.

Here’s why we could see more of the same if Trump loses in 2020.

Former Vice President Joe Biden leads his party’s 20-person pack of credible candidates with a nine-to 10-point edge over the next contender. The New York Times and other media featured a big story Friday about Biden’s latest racial gaffe.

“Poor kids are just as bright and just as talented as white kids,” Biden said Thursday during an Iowa campaign stop.

The Times’ news article said “the verbal slip-up by Mr. Biden, 76, comes as his record on race has become a central focus of the early months of the Democratic primary.”

Biden’s condescending comment Thursday suggests he has a low opinion of minorities and a high opinion of whites. By conflating economic status with race, he wrongly implies minorities are impoverished and whites succeed.

In truth, at least 10% of white children in the United States live below the federal poverty line. Most impoverished American children are white. Although minority children suffer higher poverty rates, the discrepancy is narrowing. In 2017, racial and ethnic minority children – kids the left calls “black” and “brown” – outnumbered white children for the first time in history. Someone tell Biden they are not all poor.

One could excuse Biden’s comment as a meaningless mistake, had it occurred in isolation. The statement reminds us of another Biden comment that revealed his low view of black Americans. Back in 2007, the New York Observer asked Biden his opinion of candidates for the 2008 Democratic presidential nomination. Of Barack Obama, he said: