When Mr. Bannon spoke on Thursday of “deconstructing the administrative state,” it may have sounded like gobbledygook outside the hall, but it was an electrifying profession of faith for the attendees. It is through Mr. Bannon that Trumpism can be converted from a set of nostalgic laments and complaints into a program for overhauling the government.

Mr. Bannon adds something personal and idiosyncratic to this Tea Party mix. He has a theory of historical cycles that can be considered elegantly simple or dangerously simplistic. It is a model laid out by William Strauss and Neil Howe in two books from the 1990s. Their argument assumes an 80- to 100-year cycle divided into roughly 20-year “highs,” “awakenings,” “unravelings” and “crises.” The American Revolution, the Civil War, the New Deal, World War II — Mr. Bannon has said for years that we’re due for another crisis about now. His documentary about the 2008 financial collapse, “Generation Zero,” released in 2010, uses the Strauss-Howe model to explain what happened, and concludes with Mr. Howe himself saying, “History is seasonal, and winter is coming.”

Mr. Bannon’s views reflect a transformation of conservatism over the past decade or so. You can trace this transformation in the films he has made. His 2004 documentary, “In the Face of Evil,” is an orthodox tribute to the Republican Party hero Ronald Reagan. But “Generation Zero,” half a decade later, is a strange hybrid. The financial crash has intervened. Mr. Bannon’s film features predictable interviews with think-tank supply siders and free marketers fretting about big government. But new, less orthodox voices creep in, too, from the protectionist newscaster Lou Dobbs to the investment manager Barry Ritholtz. They question whether the free market is altogether free. Mr. Ritholtz says that the outcome of the financial crisis has been “socialism for the wealthy but capitalism for everybody else.”

By 2014, Mr. Bannon’s own ideology had become centered on this distrust. He was saying such things about capitalism himself. “Think about it,” he said in a talk hosted by the Institute for Human Dignity. “Not one criminal charge has ever been brought to any bank executive associated with 2008 crisis.” He warned against “the Ayn Rand or the Objectivist School of libertarian capitalism,” by which he meant “a capitalism that really looks to make people commodities, and to objectify people.” Capitalism, he said, ought to rest on a “Judeo-Christian” foundation.

If so, this was bad news for the Republican Party. By the time Mr. Bannon spoke, Ayn Rand-style capitalism was all that remained of its Reagan-era agenda. Free-market thinking had swallowed the party whole, and its Judeo-Christian preoccupations — “a nation with a culture” and “a reason for being” — along with it. A business orientation was what donors wanted.

But voters never more than tolerated it. It was Pat Buchanan who in his 1992 run for president first called on Republicans to value jobs and communities over profits. An argument consumed the party over whether this was a better-rounded vision of society or just the grousing of a reactionary. After a generation, Mr. Buchanan has won that argument. By 2016 his views on trade and migration, once dismissed as crackpot, were spreading so fast that everyone in the party had embraced them — except its elected officials and its establishment presidential candidates.

Mr. Bannon does not often go into detail about what Judeo-Christian culture is, but he knows one thing it is not: Islam. Like most Americans, he believes that Islamism — the extremist political movement — is a dangerous adversary. More controversially he holds that, since this political movement is generated within the sphere of Islam, the growth of Islam — the religion — is itself a problem with which American authorities should occupy themselves. This is a view that was emphatically repudiated by Presidents Obama and George W. Bush.