Under Mr. Cummings’ scenario, Mr. Johnson could sit tight and schedule an election for after Brexit, sending the country crashing out of the European Union on Oct. 31 and in the middle of a campaign.

If that were to happen, it would run afoul of the civil-service code, which forbids any major policy changes during an election campaign, on the assumption that an incoming government would want to have its say on the matter.

There is considerable debate about whether Mr. Johnson is really planning to hop the constitutional guardrails or is simply threatening to do so for the sake of political leverage.

He may be trying to persuade European leaders to offer friendlier terms on a new Brexit deal by showing that he is serious about leaving without one, analysts say. And he may be trying to show British lawmakers the folly of trying to boot him from office, given the threats that he would ignore them anyway.

Others have said that if Mr. Johnson is sincere in his threats to call a general election and crash out of the European Union on Oct. 31, that could mean conducting a campaign in the midst of economic chaos, shortages of food and medicine, and secession threats in Scotland and Northern Ireland — not exactly the most attractive political terrain for the incumbent Conservatives.

Perhaps that is what Dominic Grieve, a Conservative lawmaker and former attorney general, had in mind when he called the idea of Mr. Johnson squatting in Downing Street “breathtaking, stupid, infantile, and it won’t work.”