Boris Johnson’s ascent to the Tory leadership now looks unstoppable, judged by nervous fellow MPs to be the candidate best placed to vanquish the Brexit party by adopting their central demand for a no-deal Brexit. The apparent inevitability of his ascent has led careerist critics like Matt Hancock to ditch their principles and climb aboard, driven by the animating force of self-interest. Johnson emerged strengthened by the latest ballot and will be tested against other candidates for the first time in tonight’s leadership debate. Dominic Raab was eliminated having offered much the same Brexit position as Johnson but without his political agility.

The other story is the momentum building behind Rory Stewart – despite passing the threshold required to proceed in the contest by only four votes. A reputed former MI6 officer who went to the same school (Eton) and same Oxford college (Balliol) as Johnson, Stewart is a very Tory insurgent. Against all expectations, he remains in the race and is now four votes ahead of Sajid Javid and just four votes behind Michael Gove. Yet even if he were to make it to the final two who will go forward for a ballot of all members, polling suggests that Johnson remains the overwhelming favourite.

Even though Stewart has little chance of winning, he has still reshaped the race. By relentlessly exposing the deceit of his fellow candidates, Stewart’s campaign leaves Johnson weakened as he heads towards the realisation of his only guiding principle: the ambition to be prime minister. Stewart has been very effective at exposing the lie that the withdrawal agreement can be renegotiated through force of personality. He has made plain that a plan predicated on renegotiating it is in truth a plan for a no-deal exit at the end of October. As the Institute for Public Policy Research progressive thinktank has pointed out today, there are still 10 major questions that no-deal advocates have been unable to answer, from fishing to trading agreements.

What’s more, the style of Stewart’s campaign has been an implicit rebuke to Johnson. By speaking with clarity and sincerity and engaging with the public and journalists, Stewart has thrown the mendaciousness and evasiveness of Johnson into sharp relief. This means that Johnson will seize a tarnished crown if he succeeds in his bid for the premiership. If this damage to the frontrunner is sustained, then it may cause Johnson to alter course away from a drive towards a snap general election in the autumn ahead of a no-deal exit at the end of October.

Ultimately, Stewart’s campaign is unlikely to change the result: Johnson remains on course to win both the parliamentary contest and the membership ballot. While Stewart’s campaign has revealed the level of latent support in the media and among the public at large for traditional conservatism that preserves the status quo rather than the radical right that seeks to upend it, recent polling has shown that Tory members have become possessed by Brexit demons. So determined are they to leave the EU that they say they are willing to crash the economy, break the union and destroy the Conservative party to do so. The tag team of Theresa May, Johnson and Nigel Farage has generated an insatiable thirst for a no-deal Brexit, no matter the cost.

Nonetheless, it is worth recalling that Stewart’s central proposition is to revive May’s withdrawal agreement, which went down to the greatest defeat in parliamentary history. For all the damage Stewart has done to a future Johnson premiership, he still advocates for a Brexit far from the fantasies of 2016 and whose principal purpose is the survival of the Conservative party, rather than the interests of the country. And for that, he still deserves opprobrium rather than praise.

• Tom Kibasi is director of the Institute for Public Policy Research and chair of the IPPR Commission on Economic Justice