Paul Krugman highlights how the politics of the Republican party are mainly about privileged white men feeling like they're losing their privilege:
There have been many studies of the forces driving Trump support, and in particular the rage that is so pervasive a feature of the MAGA movement. What Thursday’s hearing drove home, however, was that white male rage isn’t restricted to blue-collar guys in diners. It’s also present among people who’ve done very well in life’s lottery, whom you would normally consider very much part of the elite.
In other words, hatred can go along with high income, and all too often does.
At this point there’s overwhelming evidence against the “economic anxiety” hypothesis — the notion that people voted for Donald Trump because they had been hurt by globalization. In fact, people who were doing well financially were just as likely to support Trump as people who were doing badly.
I very much ran with the nerds during my own time at Yale, but I did encounter people like Kavanaugh — hard-partying sons of privilege who counted on their connections to insulate them from any consequences from their actions, up to and including abusive behavior toward women. And that kind of elite privilege still exists.
But it’s privilege under siege. An increasingly diverse society no longer accepts the God-given right of white males from the right families to run things, and a society with many empowered, educated women is finally rejecting the droit de seigneur once granted to powerful men.
And nothing makes a man accustomed to privilege angrier than the prospect of losing some of that privilege, especially if it comes with the suggestion that people like him are subject to the same rules as the rest of us.
This basic dynamic explains almost every revolution in history, including the American one in the 1770s. This time it's white men, but it could be any elite group who start losing power. The Post makes a similar point:
Jennifer Palmieri, a Democratic strategist and author of “Dear Madam President,” a book about reimagining women in leadership roles, said the nation’s fast-changing culture can be unsettling and indeed frightening to men in power.
“A lot of white men don’t know what it’s like to feel threatened, powerless and frustrated,” said Palmieri, former communications director for Clinton’s campaign. “As we go through the reckoning of this lopsided power balance, there’s going to be a lot more of this.”
The Republican Party has long identified with more traditional white males, such as former presidents Ronald Reagan and George W. Bush. But strategists say it is now turning more toward combative male candidates in the mold of Trump, with allegations of misconduct interpreted by many within the party not as liabilities but as unfair political attacks.
“We’re a party of angry, older white men at a time when our country is going through tremendous demographic change,” Republican strategist John Weaver said, predicting that the GOP would suffer the consequences in future elections.
So when white voters tell pollsters and reporters that they fear a tide of "those people" coming over the border, they feel afraid of losing their birthright. Not the traditions and culture, necessarily, but the parts of those things that put them on top because of the accident of birth.