Rory Stewart has been ousted from the Conservative leadership contest after losing 10 votes since the last round, sparking MPs’ speculation that Boris Johnson’s operatives may have previously pushed fellow supporters to vote for the outsider to help eliminate his Brexiter rival Dominic Raab.

Rory Stewart knocked out of Tory leadership contest in third round - live news Read more

Stewart was leapfrogged by Sajid Javid, who increased his support by five votes to stay in the race. The home secretary’s team insisted the momentum was now with him as the insurgent after his defeated rival underperformed in the TV hustings on Tuesday night.

“Saj has always had a funny habit of defying the odds,” one campaign ally said.

One former cabinet minister denied Raab had been the victim of a plot, but conceded that Johnson’s right-hand man, Gavin Williamson, may have “bullied a few weak souls into transferring their allegiance” in order to knock the former Brexit secretary out of the race.

Stewart said he would not dwell on how he had lost the votes. “All sorts of things might be happening in strange secret ballots,” he said. “But in the end the question for our country is bigger than that.”

Williamson, the former defence secretary and chief whip, has been one of the key whips for Johnson’s campaign.

In the third round of voting on Wednesday, Johnson substantially increased his tally to 143 votes, almost three times the number of his closest rivals Jeremy Hunt (54) and Michael Gove (51).

The chancellor, Philip Hammond, will launch a broadside at Johnson in a speech on Thursday, when the former foreign secretary is expected to be confirmed as one of the final two candidates.

Hammond will say any Conservative prime minister pursuing a no-deal Brexit would put at risk every party value, the union, economic prosperity and a general election.

“I will not concede the very ground we stand on,” he will say in the charged speech at Mansion House. “I will fight, and fight again, to remake the case for pragmatism and, yes, for compromise in our politics – to ensure an outcome that protects the union and the prosperity of the United Kingdom.”

He will also warn candidates there will be no funds for any of their spending commitments if a no-deal Brexit occurs.

Backers of Raab, the former Brexit secretary, flocked almost en masse to Johnson on Wednesday. Raab endorsed Johnson in the morning and by the time voting had begun at 3pm, 14 of his 30 supporters had declared for Johnson.

One of Raab’s former supporters insisted Stewart’s performance in the BBC hustings had been his downfall, rather than any dark arts of a leadership rival. “Colleagues were interested in putting him through to the debate to see him take on Boris. But he admits he made a mistake, he tried to act the statesman, he didn’t go for Boris,” the MP said.

Another former minister confided he had backed Stewart in the last round to see him take on Johnson, but had then switched to support Gove.

An ally of Stewart said the international development secretary had been torn over text messages he had received from fellow MPs asking him to tone down his attacks, causing him to doubt his strategy.

Stewart publicly admitted his performance in the BBC debate, in which candidates often talk over each other in a battle for airtime, had not been sure-footed.

Brexiters were gleeful about Stewart’s ousting. Andrew Bridgen said: “It is reassuring that there are just 27 of my colleagues who are completely bonkers.”

Javid, Gove and Hunt will be keen to gain Stewart’s supporters. Amber Rudd, the work and pensions secretary who is backing Hunt, hosted a dinner on Wednesday night for the One Nation group of Tory moderates, of which Stewart is a founder member.

Johnson’s backers have privately made it clear that they would prefer to face Hunt in the final round and avoid the “psychodrama” of facing Gove, who triggered Johnson’s exit from the 2016 leadership race, though it is unlikely such a successful tactical voting operation could be mounted against the environment secretary, and one campaign source conceded Stewart’s votes are likely to scatter.

One of Gove’s backers, Nicky Morgan, said she believed any efforts to manipulate the final two “will go down very badly with Tory MPs and members ... the obvious motivation for keeping Michael off the ballot is to avoid a competitive race and a real contest of ideas”.

Javid’s team insisted he would not be pulling out of the race, and denied he had borrowed votes to oust Stewart. “Saj has never borrowed anything from anybody,” said one adviser.

His team plans to woo Stewart’s supporters by stressing their common characteristics and the home secretary was the first to praise his rival after the results came in.

“Rory acts differently, talks differently, speaks to different audiences, and that’s a message that he and Saj absolutely share,” the source said. “As we move forward into tomorrow we think we can talk to those MPs. Saj has been written off his entire life, but we think we can do it again.”

Johnson added 17 more MPs to his tally. However, key members of the European Research Group (ERG) of hard Brexiter Tory MPs have begun issuing coded warnings to the frontrunner about the limits of their support.

Members of the group were reportedly alarmed by Johnson’s refusal to be drawn on offering any guarantee of the UK leaving the EU on 31 October beyond saying it was “eminently feasible”.

His evasiveness was highlighted by Hunt, who told the BBC on Wednesday: “Boris has made a big play of saying we’ll leave, deal or no deal, on October 31. Yesterday, frankly, he suggested he wouldn’t be so absolute in that,” Hunt said. “I’m not entirely sure what he believes on this.”

Johnson’s backers, including Liz Truss, the chief secretary to the Treasury, and Steve Baker, the deputy chair of the ERG, insisted in broadcast interviews and on social media that they had guarantees the UK would exit by that date.

One prominent Brexiter, when asked what would happen to Johnson if he reneged on his pledge that the UK would be out by 31 October, said: “The same thing that happened to Theresa May – only a lot quicker.”

Johnson’s rivals have openly questioned how he can be keeping the support of soft-Brexit Tories, including the health secretary, Matt Hancock, and the former deputy prime minister Damian Green, as well as no-deal Eurosceptics, such as Baker and Mark Francois.

Conservative MPs will vote again on Thursday morning and, if necessary, in the afternoon to deliver the final two candidates who will go on to the ballot paper to Conservative members.