Jonathan Chait has a theory about why Donald Trump’s success took him and other pundits by surprise: “The Republican Party turns out to be filled with idiots. Far more of them than anybody expected.”

But Chait’s idea is singularly unhelpful. It actually helps absolve Trump supporters of responsibility: Idiots are usually not held accountable for their acts.

Thankfully, we have actual data on Trump’s supporters. Far from being idiots, they are people who would normally be considered functioning and successful. Trump’s supporters are better educated and wealthier than the American average.

Rather than characterizing them as losers who are easily fooled, Trumpkins deserve to be looked at in their own terms. Donald Trump’s essential appeal is based on racism.

Trump launched his campaign talking about Mexican “rapists,” and subsequently stirred up xenophobia against many other groups, especially Muslims. His racist pitch succeeded because the Republican Party is overwhelmingly white and has relied heavily on dog-whistle appeals to racism since the early 1960s.

He is appealing to the aggrieved privilege of well-to-do white Republicans who feel threatened by America’s changing demographics and challenges to the traditional racial hierarchy in the age of Obama.

They aren’t being fooled by Trump. They know what he’s selling and they like it.