Labour’s legislation to prevent him from withdrawing without a deal, Mr. Johnson said, amounted to a “surrender bill” to Europe. He branded it a strategy of “dither and delay,” repeating the phrase like it was a poll-tested message for a campaign.
For his part, Mr. Corbyn complained that Mr. Johnson refused to answer questions about the economic costs of a no-deal Brexit. The government, he said, declined to release an internal study, known as Operation Yellowhammer, which he said presented a dire picture of food and medical shortages.
“He’s desperate, absolutely desperate, to avoid scrutiny,” Mr. Corbyn declared. “If the prime minister does to the country what he did to his party over the last 24 hours, a lot of people have a great deal to fear.”
That line drew blood: Mr. Johnson’s purge the previous day has left the Conservative Party in a state of near-civil war. The prime minister watched on Tuesday as one of his members crossed the House floor and sat with the Liberal Democrats, officially erasing his government’s one-seat majority. The subsequent expulsions left the government 21 seats short of a majority.
For Mr. Johnson, a disheveled figure known more for his mop of blonde hair than for his legislative skills, an election would be a chance to take his case out of the gilded halls of Westminster and directly to the British public. It is a debate he won in 2016, when he led the pro-Brexit referendum campaign, and he won the party leadership this summer partly because members believed he was the best candidate to lead them into a general election.
Mr. Johnson is gambling that the Conservatives, riding slightly higher in the polls, can win a solid majority over Labour, which is mired in its own Brexit divisions and saddled with a leader, Mr. Corbyn, whose leftist views put off middle-of-the-road voters. A strong victory, he said, would allow him to go into negotiations with European officials with a stronger hand than his predecessor, Theresa May.
In the three years since the referendum, however, people here have heard harrowing accounts of what could happen if Britain leaves Europe without a deal: shortages of food and medicine; trucks lined up for miles at newly installed border posts on each side of the English Channel; chaos at airports and train stations; and violence in Ireland after a hard border once again bisects the island.