During the election, Mr. Johnson campaigned as an almost single-issue nationalist, the phrase “get Brexit done” falling robotically from his lips between every other stammer. Beyond that, much of what he said was conventionally Tory: He promised harsher restrictions on immigration, meaning an end to free movement from the European Union and the expansion of the “hostile environment” for migrants. Domestic repression, the manifesto promised, would also tighten, with a bigger penal system and a greater emphasis on “counter-extremism,” which, as Home Secretary Priti Patel has indicated, will target parts of the left. Mr. Johnson has also hinted at constitutional reforms, which would strengthen the executive and weaken judicial challenges. He promises an attack on liberal norms and legality in the name of national invigoration.

Tellingly, he distanced himself from the last government. He would end austerity, raise spending on the National Health Service, guarantee pensions, raise the minimum wage and borrow £100 billion to invest in infrastructure. Many of these promises were grossly exaggerated, but they served to underline the point that a Johnson administration would be different. And since the election, the government has acted to carry out its commitments, passing legislation to guarantee N.H.S. spending increases and proposing moderate improvements to workers’ and renters’ rights. It has also promised that most of the infrastructure spending will be invested in England’s deprived northern regions — and this week backed up the promise by nationalizing the north’s major rail service.

If this sounds like an incursion into Labour territory, it is. Many of the policies are directly taken from Labour’s plans. The push for a larger state resonates with a politically ambiguous popular memory of the postwar era — a certain nostalgia for the era of big, dynamic industries owned by the British government inflects both a version of the left-wing politics of the Labour Party leader, Jeremy Corbyn, and a version of Brexit sentiment. Mr. Johnson knows that many of the votes contributing to a Conservative majority were “lent” by voters who wanted Brexit done. A more interventionist state is a way to shore up a lasting, broad coalition.

This pragmatic raid on enemy turf was first conceived under Mr. Johnson’s predecessor, Theresa May. More thoughtful Tories knew they had to change. The British state and economy had become dysfunctional: gaping regional inequalities, a housing market inaccessible to younger workers, weak labor productivity, sluggish investment and very little to export. Mrs. May’s advisers understood that the Conservatives had to break with the formula of austerity and financialization somehow.

But while she used the rhetoric of working-class uplift, she was unable to back it up with policy. Her chancellor, Philip Hammond, a traditional ally of the banks, was determined to keep austerity going. If nothing else, he could see no other way to create a fiscal surplus big enough to soften the impact of Brexit. Mr. Johnson, by contrast, is just enough of an opportunist to see that delivering Brexit, in however self-injuring and punitive a form, gives him both the political power and the regulatory latitude to do things differently.