If you spend enough time following modern politics — and really, not very long — you will eventually hear a prediction of the left’s eventual triumph. All it needs do, the thinking goes, is wait.

Author Ian McEwan got in trouble a few years ago for making this point a little too bluntly about Brexiteers: “By 2019 the country could be in a receptive mood [for a second referendum]: 2.5 million over-18-year-olds, freshly franchised and mostly remainers, and also 1.5 million oldsters, mostly Brexiters, freshly in their graves." But some version of it, more or less explicit, is still quite popular on this side of the Atlantic: crowing about the Methuselahan demographics of the Fox News audience, predictions of the “electoral extinction” of the Republicans as a younger, hipper, more diverse “emerging Democratic majority” rises to take their place.

“Wait for the deaths of millions of your fellow citizens” is, of course, an unlovely slogan for a political movement. The only thing that can be said for it is that it’s better than “Don’t wait.” But even if you’re inclined to think it benign, you might be disturbed by the realization that it doesn’t seem to be working all that well.

After all, in 2019, Britain went back to the polls — and elected Boris Johnson, who was much more resolutely pro-Brexit than his predecessor. In the United States, the “emerging Democratic majority” of progressive whites and a growing minority population, first predicted by John B. Judis and Ruy Teixeira in 2002, has taken on a Godot-like quality. It might be time to ask whether the much-heralded demographic destiny is actually on its way.

There are three very good reasons to think not. The first is that the United States’ imminent majority-minority future isn’t quite what people assume when they hear the statistics — non-Hispanic whites are a minority of new births, with whites forecast to slip into overall minority status sometime around 2043.

That comes from a 2015 Census projection that probably didn’t fully account for what we now know to have been a collapse in Hispanic birthrates since 2008. Even more important, as sociologist Richard Alba pointed out, these numbers are to some extent an artifact of the way the census counts minority status: If you have any minority ancestry, you are “non-white.” Yet this is not how biracial children, the majority of whom have one white parent, necessarily identify themselves — or vote.

For a sense of how important that is, consider that if you reversed the census method, counting everyone with one white parent as white, Alba calculates that whites would be 75 percent of the population by mid-century.

But even people with two minority parents may not continue to identify as minorities. The old “white ethnics” — Jews and Catholics and Orthodox migrants from Europe’s economic periphery — were once considered minorities, and voted like minority groups: mainly in blocs, from highly concentrated neighborhoods. Yet today, they and all their descendants are bundled together with WASPs as white, and for good reason. There’s no reason to think that something like that assimilation won’t happen to today’s minority groups, and plenty of reasons to think that in some ways it already is happening.

All right, a nervous progressive might say, but we still have the young, and the young are strongly with us. And eventually, they’ll be the olds, and in charge.

Indisputably, but how far to the left will they be when they get there? Economist Sam Peltzman suggests not very. After examining data on political self-identification from 45 years of General Social Surveys, Peltzman found that older voters tend to be more conservative both within periods (in a given survey year, older people are more likely to say they’re conservative than younger people), and over lifetimes (people who are 65 today are more likely to say they’re conservative than were 25-year-olds in 1980). It’s not a small gap, and moreover, it keeps growing: “There is just about as much rightward drift from, say, 45 to 80 as from 25 to 45,” writes Peltzman.

Of course, what counts as a “conservative” belief can change, and has, over the decades — Republicans positioning themselves as defenders of Social Security certainly wouldn’t have done so in 1933. On the other hand, they haven’t become Debsian socialists, and there is enough continuity between decades to doubt that the United States' future looks much like today’s Democratic agenda. America is getting older, not younger, and if Peltzman is right, it means we should expect the future to be more conservative than the present.

Depending on your perspective, this is either a horrible tragedy or else just the circle of life: Today’s young progressive firebrands will indeed achieve the demographic destiny they’re looking forward to, and replace all the fogeys who stand in their way — but only by becoming them, in more ways than they currently expect.

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