Today’s central challenge is an aggressive, ascendant radical left. Incremental reform won’t counter it.

Proponents of communism often say it’s never really been tried. Progressivism can no longer make that excuse. Its doctrines are being widely implemented by earnest practitioners with wide establishment support. The results have come in with astonishing speed. Mayhem and misery at an open national border. Riot and murder in lawless city neighborhoods. Political indoctrination of schoolchildren. Government by executive ukase. Shortages throughout the world’s richest economy. Suppression of religion and private association. Regulation of everyday language—complete with contrived redefinitions of familiar words and ritual recantations for offenders.

This makes an easy case for national conservatism. Natcons are conservatives who have been mugged by reality. We have come away with a sense of how to recover from the horrors taking America down.

When the American left was liberal and reformist, conservatives played our customary role as moderators of change. We too breathed the air of liberalism, and there are always things that could stand a little reforming. We could be Burkeans—with an emphasis on incremental improvement, continuity with the past, avoiding unintended consequences, and working within a budget. In the 1970s I collaborated with liberals on regulatory reform—refining environmental policies and restraining crony capitalism. Such bipartisan pragmatism yielded many improvements.

But today’s woke progressivism isn’t reformist. It seeks not to build on the past but to promote instability, to turn the world upside-down. In 1968, Democratic mayors sided with police and prosecutors against rioters and lawbreakers. In 2020, they took the side of lawbreakers. Last year, congressional progressives not only rejected Sen. Tim Scott’s police reforms but vilified and degraded him. This year they vilify any Democrat whose spending plan is less than revolutionary. Compromise is antithetical to their goals and methods.

When the leftward party in a two-party system is seized by such radicalism, the conservative instinct for moderation is futile and may be counterproductive. Yet many conservative politicians stick with it, promising to correct specific excesses that have stirred popular revulsion. Republicans will win some elections that way—but what will they do next? National conservatives recognize that in today’s politics, the excesses are the essence. Like Burke after 1789, we shift to opposing revolution tout court.

Why national conservatism? Have you noticed that almost every progressive initiative subverts the American nation? Explicitly so in opening national borders, disabling immigration controls, and transferring sovereignty to international bureaucracies. But it also works from within—elevating group identity above citizenship; fomenting racial, ethnic and religious divisions; disparaging common culture and the common man; throwing away energy independence; defaming our national history as a story of unmitigated injustice; hobbling our national future with gargantuan debts that will constrain our capacity for action.

The left’s anti-nationalism is another sharp break with the past. Democratic presidents of previous eras—including the original progressive, Woodrow Wilson —were ardent nationalists. But in 2021 President Biden gazed on his countrymen’s epic invention of Covid vaccines and concluded that he should help the World Health Organization seize their patents.

The explanation for the break is that modern progressives imagine themselves as champions of humanity at large and the nation as a primitive artifact that constrains human aspiration and inhibits global solutions. Progressives see the downtrodden as held down by structures of systemic privilege, embedded in the nation’s traditions and institutions.

National conservatives understand that these are romantic delusions. Nations evolved organically over centuries of struggle, trial and error and acquired staying power. Man is naturally social and fraternal, and successful nations have learned how to transmute group loyalties into broader allegiance. Citizens understand that their security and freedoms depend on their nation and its imperfect institutions—that their fortunes are linked for better or worse to those of their disparate compatriots.

These circumstances give national conservatives a lot to work with. To be sure, three of the foundations of nationhood—family, religion and locality—are far weaker than in earlier times. Yet Americans remain notably patriotic. They realize that our liberties, our prosperity and our institutions of justice are rare achievements. The sense of national decline is prevalent among many American voters. If they can be persuaded that progressivism is not energetic idealism but a program for national dissolution, we may make headway.

My strategy is to show that each controversy is part of a larger movement that threatens our national ideals, institutions and stability. Consider the efforts to establish critical race theory and sexual optionality in primary and secondary schools. A great many Americans, including the prized electorate of suburban women, pay only passing attention to these weird developments when they involve adults who can fend for themselves, but rush to the barricades when they are imposed on innocent neighborhood children.

It’s a perfect case for targeted, single-issue correction—but also for illustrating the sources of national decay. The school controversies dramatize the shrinking domain of family, parenthood and religion; the pathologies of educational monopolies and teachers unions; and the cultural elites’ practice of wrapping themselves in moral virtue at the expense of the minorities they claim to be championing.

The move from criticism to nation rebuilding makes national conservatism a political movement, not simply a school of thought. We are concerned not only with the errors of our intellectual adversaries but with the circumstances of our fellow citizens. That has led us to the problems of our working-class compatriots in declining regions whose interests had been ignored in national politics and policy. We need to turn in the same spirit to the problems of our African-American compatriots in poor, violent, fatherless urban precincts. If the elites would scuttle the nation, the rest of us will have to come together to rescue it.

Many affluent, highly educated Americans who are not hard progressives are imbued with the universal humanitarianism I have mentioned. Well, we have a large and universal canvas of humanity here at home. But that humanity is our countrymen, with rights and responsibilities equal to our own. They have our empathy and support—and also our firm expectations as fellow citizens and teammates. Nationalism, properly understood, is the most potent kind of humanitarianism.

Being part of a movement can be good for us, too, as a corrective to the tendency of intellectuals to overtheorize. National conservatives hold a variety of views about our predecessors in 20th-century conservatism, neoconservatism, libertarianism and constitutional originalism. In the extreme, it is said that those isms accomplished nothing and only set the scene for our current shambles. This exaggerates the potential of ideas to affect the course of society.

I was engaged in each of those movements. We made some mistakes and compromises that might have turned out better. But we were alert to the opportunities and constraints at hand, and we got a few things right. The great prosperity of the 1980s and the luminous revival of New York City in the 1990s were the products of conservative ideas applied strategically against ferocious opposition. Originalism rescued our written Constitution from untethered judicial extemporizing and turned attention to the Founders’ principles. But we never thought our ideas were perfect, and we realized that our successes would be partial and contingent and would expose further difficulties for our successors to grapple with.

We were also aware of deep cultural changes that could overwhelm everything we were doing. Decades ago, the neocons Daniel Patrick Moynihan, Irving Kristol and James Q. Wilson published prophetic studies of the decline of marriage, family and religion, and warned that it could produce social upheavals that politics and policy would be helpless to ameliorate. Recently, a young natcon explained to me that capitalism must operate within a moral framework. “That is extremely interesting,” I said. “Have you ever heard of Michael Novak ?” “No,” he replied, “who is he? Does he do a podcast?”

It is certainly true that those forms of conservatism didn’t keep up with the times. What began as strategies designed for immediate circumstances tended to harden into overarching philosophies, glib talking points, Beltway careers. One wishes conservatism had adapted itself to new problems before they became as dire as they are. But many terrible developments—such as the pathologies of social media and the arrival of Marxian radicalism in a political system we had thought immune—were understood by practically no one until they were upon us.

So here we are. Our defining challenges are to revive our cultural and political institutions, reintroduce a morally informed common culture, recast America’s role in world security, and revise the social compact of business and government. A tall order! Let me offer a few observations from the standpoint of a free-market man.

I have been a libertarian since I was a little boy and noticed the label on my mattress: “Do Not Remove Under Penalty of Law.” But then, as a young man, I attended my first capital-L Libertarian conference, where people were wearing buttons that said “Freedom Is My God” and “There Is No Such Thing as Society.” These were as frightening as the mattress label, and I sought a middle ground that balanced freedom with virtue, markets with society, and recognized that you can’t have one without the other.

I settled on empirical libertarianism, which considers each policy on the merits but in the spirit of Adam Smith : Government interventions “ought never to be adopted till after having been long and carefully examined, not only with the most scrupulous, but with the most suspicious attention.” I also understood that freedom, although grounded in human nature and God’s design, is in practice an artifact of government. Property and contract, freedom of speech and religion and commercial competition, separation of powers, due process of law—all were introduced and calibrated through centuries of piecemeal conflict and resolution. Government is at once the source of our freedoms and their most dangerous enemy.

We face the need to rebalance freedom and virtue, market and society. Private enterprise is the source of cornucopian blessings, but it needs boundaries and discipline. It has become a willing accomplice of cultural decline and has developed global markets that eclipse the nation and divide its citizens. These developments are largely the result of modern technology, not any political doctrine, but they demand political responses.

Here national conservatives face a dilemma that is well known to empirical libertarians: How can government reform the society it is designed to represent and protect? Government and markets are both mechanisms for interpreting prevailing interests and preferences. But government is more responsive to large, well-connected groups and tends to entrench them—its responses are less open to challenge and adaptation than the market’s. This problem is exacerbated by today’s “executive state,” a particularly uncongenial setting for national conservatives. It consists of a profusion of special-purpose bureaucracies with little ability to discern, articulate or pursue the common good.

One approach is to start with the tried and true. Facebook and other powerful network czars are going to be regulated in some fashion, and the common-carrier obligation has a long pedigree in Anglo-American law. Americans have excelled at big, bureaucracy-busting projects in science and engineering, most recently Operation Warp Speed. Cybersecurity and quantum computing are prime candidates for such national mobilization, and this could do much to redomesticate production in critical fields. Self-help is another American specialty. Our once-great universities and museums were established by private initiative. We are a rich nation and could do that again.

Another strategy is to direct our reformist energies at our decrepit political institutions themselves, aiming to make them more attentive to the state of the union rather than to yesterday’s polls and tweets. This is my own field, where I think much can be accomplished within our constitutional structure and traditions. The originalist in me notes that the president is not only CEO of the executive bureaucracies but also, and primarily, head of state, responsible for the nation’s success and all of its citizens’ welfare.

National conservatism, not Marxian progressivism, is today’s vanguard. My own motto for national conservatism is another extrapolation from Adam Smith: There is a great deal of ruin in a nation, especially these days—but also a great deal of repair, especially in America.

Mr. DeMuth is a distinguished fellow at the Hudson Institute. This article is adapted from a Nov. 1 speech at the National Conservatism Conference, which he chaired.