If all candidates pass the 33-vote threshold, the one with the lowest total will be eliminated and by the end of the week, four of the six current riders will be forced out, leaving the final two to go head-to-head for votes from the Tory grassroots. While he has vowed to respect the October 29th Brexit day while others - including Michael Gove - have said they would consider delaying Brexit again, Nigel Farage has raised doubts about Johnson's dedication and reliability.
We can stop a no-deal Brexit much more easily than that.
His campaign has gathered momentum and won the backing of de facto deputy prime minister David Lidington, but he faces a hard task to overhaul the vote tallies of rivals.
The final two names will then be put to a postal vote of the 160,000 Tory party members, beginning on 22 June, with the victor expected to be announced about four weeks later.
"That's where I have my strongest appeal, as that broad appeal", he said.
But parliament has indicated it will try to stop a no-deal Brexit, which investors warn could roil markets and shock the world economy, while the European Union has said it will not renegotiate the Withdrawal Agreement that May agreed.
The House of Commons was the route out of the impasse, he argued: "I'm the only person trying to find the key, everyone else is staring at the wall shouting "believe in Britain", he said.
He told Mr Gove and Mr Hunt: "We have got to learn from our mistakes".
Mr Hunt aimed his fire at Mr Johnson as he asked about a sheep farmer in Shropshire whose business would be destroyed by the extra tariffs from a no-deal Brexit. Who do you think took the crown? "He would say, you [Mr Johnson] got your dream of getting into Number 10, but what about my dream, to have a family business?"
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The small forward, however, is nearly certain to opt out of the final year of his deal and become an unrestricted free agent next month.
Mr Johnson is the frontrunner in the Tory leadership race which is in full swing.
The event was chaotic, with numerous candidates speaking over each other and struggling to articulate their policy platforms.
However, they largely agree on cutting taxes for the working classes, apart from Stewart, who said was "this is not the time for tax cuts".
Sajid Javid, the Home Secretary, who was also a former Remainer, said too that he would vote Leave if offered a second chance.
Mr Stewart almost doubled his backing, albeit from a low base, to 37 votes to stay in the competition on Tuesday afternoon.
Jeremy Hunt repeated his second place finish from last week but he too only managed to increase his haul by three votes as he went from 43 to 46 while Michael Gove went from 37 to 41.
At the debate, the four other candidates - after former Brexit minister Dominic Raab was knocked out - tried to test Johnson, a former London mayor who has so far been relatively silent in the campaign, even avoiding an earlier debate.
Both Mr Johnson and Dominic Raab have insisted that they are ready to lead Britain out of the European Union with or without an agreement on 31 October.
All five ruled out the idea of a general election before Britain has left the EU.