Remember Paul Ryan? The speaker of the House used to be a media darling, lionized as the epitome of the Serious, Honest Conservative — never mind those of us who actually looked at the numbers in his budgets and concluded that he was a con man. These days, of course, he is overshadowed by the looming Trumpocalypse.

But while Donald Trump could win the White House — or lose so badly that even our rotten-borough system of congressional districts, which heavily favors the G.O.P., delivers the House to the Democrats — the odds are that come January, Hillary Clinton will be president, and Mr. Ryan still speaker. So I was interested to read what Mr. Ryan said in a recent interview with John Harwood. What has he learned from recent events?

And the answer is, nothing.

Like just about everyone in the Republican establishment, Mr. Ryan is in denial about the roots of Trumpism, about the extent to which the party deliberately cultivated anger and racial backlash, only to lose control of the monster it created. But what I found especially striking were his comments on tax policy. I know, boring — but indulge me here. There’s a larger moral.

You might think that Republican thought leaders would be engaged in some soul-searching about their party’s obsession with cutting taxes on the wealthy. Why do candidates who inveigh against the evils of budget deficits and federal debt feel obliged to propose huge high-end tax cuts — much bigger than those of George W. Bush — that would eliminate trillions in revenue?

And economics aside, why such a commitment to a policy that has never had much support even from the party’s own base, and appears even more politically suspect in the face of a populist uprising?

But here’s what Mr. Ryan said about all those tax cuts for the top 1 percent: “I do not like the idea of buying into these distributional tables. What you’re talking about is what we call static distribution. It’s a ridiculous notion.”

Aha. The income mobility zombie strikes again.

Ever since income inequality began its sharp rise in the 1980s, one favorite conservative excuse has been that it doesn’t mean anything, because economic positions change all the time. People who are rich this year might not be rich next year, so the gap between the rich and the rest doesn’t matter, right?

Well, it’s true that people move up and down the economic ladder, and apologists for inequality love to cite statistics showing that many people who are in the top 1 percent in any given year are out of that category the next year.

But a closer look at the data shows that there is less to this observation than it seems. These days, it takes an income of around $400,000 a year to put you in the top 1 percent, and most of the fluctuation in incomes we see involves people going from, say, $350,000 to $450,000 or vice versa. As one comprehensive survey put it, “The majority of economic mobility occurs over fairly small spans of the distribution.” Average incomes over multiple years are almost as unequally distributed as incomes in any given year, which means that tax cuts that mainly benefit the rich are indeed targeted at a small group of people, not the public at large.

And here’s the thing: This isn’t a new observation. As it happens, I personally took on the very same argument Mr. Ryan is making — and showed that it was wrong — almost 25 years ago. Yet the man widely considered the G.O.P.’s intellectual leader is still making the same old claims.

O.K., maybe I’m just indulging a pet peeve by focusing on this particular subject. Yet the persistence of the income mobility zombie, like the tax-cuts-mean-growth zombie (which should have been killed, once and for all, by the debacles in Kansas and Louisiana), is part of a pattern.

Appalled Republicans may rail against Donald Trump’s arrogant ignorance. But how different, really, are the party’s mainstream leaders? Their blinkered view of the world has the veneer of respectability, may go along with an appearance of thoughtfulness, but in reality it’s just as impervious to evidence — maybe even more so, because it has the power of groupthink behind it.

This is why you shouldn’t grieve over Marco Rubio’s epic political failure. Had Mr. Rubio succeeded, he would simply have encouraged his party to believe that all it needs is a cosmetic makeover — a fresher, younger face to sell the same old defunct orthodoxy. Oh, and a last-minute turn to someone like John Kasich would, in its own way, have similar implications.

What we’re getting instead is at least the possibility of a cleansing shock — of a period in the political wilderness that will finally force the Republican establishment to rethink its premises. That’s a good thing — or it would be, if it didn’t also come with the risk of President Trump.