Over the past decade and a half, tolerance for polygamy has more than doubled among the American public. A similar trend applies to human cloning.

Stunning as they are, these findings from the latest Gallup survey of moral opinion in the United States may tell more about the political future than the daily drama surrounding Donald Trump.

To be sure, the percentage declaring polygamy and human cloning “morally acceptable”, in Gallup’s phrase, remains small: 17 per cent are OK with the former; 14 per cent the latter. Neither is likely to become legal soon.

Yet the speed with which these formerly fringe ideas have moved towards the mainstream is significant and consistent with Gallup’s broader finding: since 2001, there has been a clear and, apparently, irreversible, move towards more permissive, or, to use Gallup’s word, “liberal” social norms.

“Libertarian” may be a better term. Gallup documents what can only be called a strong live-and-let-live consensus regarding several practices — birth control, divorce, sex between unmarried adults, gay or lesbian relations, out-of-wedlock child-bearing — that within living memory were either fiercely contested or taboo. All garnered at least 62 per cent acceptance in the poll, conducted just a month ago. Doctor-assisted suicide is trending up and now stands at 57 per cent acceptance.

Taboos are weakening against pornography (acceptance up six points to 36 per cent since 2011) and sex between teenagers (acceptance up four points to 36 per cent since 2013). Meanwhile, new taboos are developing against wearing fur and medical testing on animals. Only adultery remains as unacceptable as in 2001; just 9 per cent tolerate it.

In short, the culture wars may be ending in victory for progressives, with the caveat that a Left-Right frame is misleading regarding some issues — opposition to pornography, for example, has at times been a rare point of agreement between the religious Right and left-wing feminists.

Americans are not only far more willing to countenance formerly taboo practices, they are also much less interested in government protection of “traditional values” than they were in the not-so-distant past.

It has been six years since another poll, by CNN/ORC, found for the first time that more Americans said the Government should “not favour any set of values” rather than “promote traditional values”.

As of the most recent poll, in late 2014, 55 per cent preferred a value-neutral government. No one would have predicted that just after the September 11, 2001 terrorist attacks, when CNN/ORC found that 59 per cent of Americans favoured government promotion of traditional values, an all-time high.

Maybe that galvanising moment gave way to the multiple disappointments and disillusions of the Iraq war and the financial crisis, which in turn bred broader doubts about government’s ability to do anything right, let alone foster moral values, and perhaps about the values themselves.

Another explanation, though, is that Gallup’s numbers confirm a longstanding post-war trend first identified by political scientist Ronald Inglehart of the University of Michigan, who has argued that Western societies’ turn from traditional values to individual autonomy and self-expression reflects their growing economic security, notwithstanding periodic wars and recessions.

The satisfaction of basic material needs, on a consistent basis, provides time and space for cultural, sexual and spiritual experimentation. Conversely, Inglehart has argued, members of society who feel least secure, materially and otherwise, continue to derive meaning from tradition and react against perceived threats to it emanating from the political sphere.

One interpretation of the overwhelming support of the country’s most religious, tradition-minded voters for a thrice-married, hedonistic tycoon is that it demonstrates their desperation to stop the progressive cultural wave. Another, of course, is to reduce it to racist and nativist backlash.

Then again, data from Gallup and other sources show such wide moral acceptance of non-traditional norms that the new consensus must include plenty of Trump voters as well. The main exceptions to that consensus are abortion and gun control, about which a relatively even and highly partisan divide persists — and which candidate Donald Trump exploited to win over red-state voters who might otherwise have distrusted him.

That suggests our partisan battles over abortion and guns are far from over. Otherwise, social-issue politics could be increasingly a matter of managing the new consensus — setting the conditions for doctor-assisted suicide, say, as opposed to debating its permissibility. That could facilitate a soft landing from the present instability.

This bizarre moment in American politics reflects the desperate effort by all concerned — voters, parties, politicians, journalists — to find our footing in a postmodern world we inescapably inhabit but poorly understand. Trump’s rise is a cause of this predicament, but also a symptom of it.

•Charles Lane is a Washington Post editorial writer, specialising in economic and fiscal policy, a weekly columnist, and a contributor to the PostPartisan blog