Zohran Mamdani’s campaign is driving some people mad.

Mamdani is, of course, the young, charismatic, charming and decidedly left-of-center candidate upsetting the political status quo. He is also Muslim and of Indian and Ugandan descent. The recent political attacks against him are coming from all directions — Republicans, Democrats and the real estate lobby. Some of these attacks are about political interests — of course, landlords wouldn’t like affordable housing and tenant-friendly Mamdani.

But a lot of these attacks are thinly veiled racism. They conflate Mamdani’s left-wing political messaging with the “otherness” of his racial and ethnic heritage. It is an old racial trope that worked unevenly against President Barack Obama. Be afraid of the cheerful brown man. He isn’t a “real” American. He is dangerous because he wants to take from the rich to give to the undeserving poor.

It makes sense that Republicans play this card. They already dally in the irrational world of race fantasy, where white Americans are an oppressed majority. But Democrats are supposed to know better. Being the party that knows that race is real, that it works in measurable ways and that those ways matter to their base is kind of their brand. They had it figured out when these attacks were deployed against Obama.

If they knew it was wrong in Obama’s case, why are they falling for it in Mamdani’s?

For one answer, look to our current political and demographic moment. Americans are more diverse than they were 50 years ago. A combination of migration and changing norms around love and marriage means that the nation has become — and will continue to become — less white.

A primal fear of minorities drove a lot of voters toward Donald Trump. It should be commonly accepted by now that his political rhetoric targets minorities and uses violent stereotypes to dehumanize them and that millions of his supporters don’t just accept that — they relish it.

But at the same time, Donald Trump managed to appeal to some racial minorities during this last election. That caused liberals and poll watchers a lot of angst. How can anyone explain his support among the very racial and ethnic groups that he endangers?