The fact that Mr. Bannon serves simultaneously as, in the journalist Ben Smith’s words, “the guy selling a new cross-racial coalition” and “the chief arsonist of that coalition” casts suspicion about how seriously to take his pronouncements. Nevertheless, political science research confirms that large numbers of Americans hold positions on issues that are both noncentrist and inconsistent with the standard line of either modern-day liberalism or conservatism. At least some raw material exists, in other words, for a transformation of party conflict.

A single election sweeping an unorthodox candidate into power hardly suffices. President Trump’s evident disinterest in even trying to reorient Republican governance away from priorities like welfare state retrenchment and regressive fiscal policy underscores the point. Mr. Bannon says he knows that realignments are something activists will have to “grind out day in and day out for the next five, 10, 15, 20 years.”

What he thinks those years of effort entail is less clear. Investment in candidate recruitment and nomination challenges would be one component. On that score, though, the lack of consistent issue or ideological patterns in the challengers that Mr. Bannon has touted so far for 2018 is notable.

Even more important would be the long-term intellectual work and institution-building necessary to build political alliances among existing or emerging groups. The tweedy quarterly American Affairs presents itself as the high-level intellectual exponent of Trumpism, while Breitbart provides day-to-day red meat in the form of trolling, outrage and race-baiting cultural politics.

Mr. Bannon’s one institutional reform goal in the 2018 challenges invites further skepticism. He has said he’s seeking a Republican Senate majority that would vote to do away with the filibuster, making it easier to pass Mr. Trump’s agenda. This ignores the reality that even in the event of a filibuster abolition, the agenda helped would be orthodox Republican — like the current tax cut bill — reflecting the priorities of the interests that dominate the party and the policy expertise of the Heritage Foundation veterans who staff the executive branch under Mr. Trump.

By contrast, a serious pursuit of reforms that could advantage “populists” might include changes to the campaign finance system, which currently facilitates the very party dominance by plutocrats that Mr. Bannon denounces.

If the potential is out there in the electorate to reshuffle the deck of political alliances and conflict, how would a serious realigner actually do it? Such a person might look at the very realignment that produced our current, polarized age.