The opening salvo came unexpectedly in an unlikely setting. Donald Trump, appearing at the National Association of Black Journalists’ convention, thought it’d be a good idea to go after Vice President Kamala Harris on race.

“She was always of Indian heritage, and she was only promoting Indian heritage,” the Republican presidential nominee said of his likely opponent on the Democratic side. “I did not know she was Black until a number of years ago when she happened to turn Black, and now she wants to be known as Black.”

In case that wasn’t quite enough, the former president added, “I respect either one, but she obviously doesn’t, because she was Indian all the way, and then all of a sudden, she made a turn and … she became Black. … Somebody should look into that, too.” Trump concluded: “Is she Indian, or is she Black?”

The backlash was immediate — and widespread. Even some Republicans described the GOP nominee’s racism as “embarrassing” and “awful.” An Axios report described Trump’s offensive as “a nightmare” for his party.

But let’s not lose sight of the fact that Trump’s new line of attack wasn’t limited to the stage in Chicago. After the event, he used his social media platform to push a follow-up salvo. “Crazy Kamala is saying she’s Indian, not Black,” he wrote alongside a video of Harris referencing her Indian heritage. “This is a big deal.”

Soon after, ahead of a campaign rally in Pennsylvania, Trump’s political operation promoted images on a giant screen featuring headlines noting Harris’ Indian-American identity.

On Thursday morning, as NBC News noted, the Republican nominee pushed the line of attack again.

A day after attacking the vice president race during a contentious interview with Black journalists, Trump posted a picture on his Truth Social website of Harris wearing a saree alongside members of her family. Trump and his allies have falsely accused Harris, who is biracial, of deciding to “turn Black.” Harris, the first Black and Indian American vice president, attended the historically Black Howard University and is a member of the first intercollegiate Black sorority, Alpha Kappa Alpha.

This, evidently, is Trump’s idea of a gotcha.

So, why in the world is he doing this? I won’t pretend to have any special insights into the former president’s weird perspective, but the answer isn’t immediately obvious.

It’s possible that Trump thinks he can convince Black voters that Harris isn’t Black enough. Or maybe Trump thinks it’s up to him, and not Harris, to decide how she should describe her own race and ethnicity.

It’s also possible that Trump, whose lengthy record of overt racism is well documented, is genuinely confused about the very idea of someone being biracial. If Harris has celebrated her mother’s background, as far as the Republican sees it, it necessarily means she rejected her father’s background.

Or maybe Trump’s brand of racism is based in part on the idea that those in communities of color get special breaks and benefits, making him uncomfortable with the idea of an opponent being able to check more than one box.

Whatever the explanation, it seems like a safe bet that voters haven’t heard the last of this line of attack, even if many GOP officials would prefer to hear Trump say anything else.

UPDATE (August 1, 2024, 2:26 p.m. ET): Shortly after I published this piece, Trump used his social media platform to amplify a related online item from right-wing media personality Laura Loomer, who claimed that Harris’ birth certificate “proves” that she’s not Black.