The day I first realised that Jacob Rees-Mogg could be prime minister was 12 July 2017. The time was 7.30pm, the occasion was the election of a new chair for the Treasury select committee. The rules of select committee chairs are simple: the number allocated to each party is calculated based on their performance at the previous general election. Candidates must be from the party allocated but all MPs get to vote.

For the most part, MPs tend to divide the votes of their own party fairly evenly, with the votes of others the decisive factor. That’s one reason why select committee elections tend to reward relative centrists or those who have worked across party lines. Perhaps an ideological firebrand could overcome that if he or she were chair of a particularly popular all-party parliamentary group, such as the APPG for Jazz Appreciation, one of the few causes capable of bringing together Alison Thewliss, the SNP MP for Glasgow Central, with Ian Paisley Jr, the DUP MP for North Antrim. Even then, for the most part, select committee elections are contests in which only moderates need apply for the top job.

So Rees-Mogg’s bid for a post considered to be one of the most important select committee posts in Westminster was always expected to fail: he is no one’s idea of a moderate and has largely eschewed the more socially popular APPGs. To add to his difficulties, his opponent, the liberal Tory Nicky Morgan, in addition to being more ideologically congenial to Labour MPs, had made numerous friends and allies in other parties because of her work on the Remain campaign and its successor organisation, Open Britain. Yet, in the end, while Morgan won, she did so only by 64 votes, taking 290 to Rees-Mogg’s 226. Considering that, to my knowledge, Rees-Mogg can scarcely have attracted the votes of a dozen Labour MPs and perhaps another dozen from other parties, he must have won, and won well, among Tory MPs.

Of course, a select committee chairmanship and being prime minister are very different. A critical mass of Conservative MPs will always recoil from the notion of putting someone who has never reached cabinet rank straight in at No 10. Should Rees-Mogg put himself forward for the Conservative leadership, as many expect, he won’t get anything close to 226 votes from the parliamentary party. But he doesn’t have to: under the rules, the role of MPs is to winnow down the list of candidates to two survivors, who then compete for the votes of members. Andrea Leadsom made it to the final two with the support of just 84 MPs, and several Conservatives believe that Rees-Mogg could reach a similar figure.

Although the Leadsom of 2016 and Rees-Mogg of today have much in common – they are both committed Brexiteers who have or had never held cabinet rank – the differences are just as important. When Leadsom ran in 2016, she was taking part in the honourable tradition of running not to win but to establish her credentials for a cabinet post in the immediate aftermath. Only the implosion of Boris Johnson and Michael Gove meant that she did as well as she did.

If Rees-Mogg decides to run, he starts in a very different position: he is, as far as the bookmakers are concerned, already the frontrunner. Most Conservative MPs are ideologically closer to David Cameron than they are to Theresa May, and are light years away from Rees-Mogg, who is a deeply religious social conservative.

Tactical voting has always been a feature of Tory leadership contests, and Rees-Mogg’s undoubted appeal among the grassroots means that his most ardent opponents will be desperate to prevent him reaching the final two, even if that means elevating another candidate whose politics they dislike, such as Johnson. Yet Rees-Mogg is on the rise, in part because he shares some of Jeremy Corbyn’s qualities: the Labour leader will play a more significant role in the next Tory leadership contest than any rival politician since Tony Blair in 2005, when Cameron consciously pitched himself as the party’s answer to the man who had defeated them three times.

Although Corbyn has not yet defeated the Tories, the lost majority of 2017 has had a similar effect on party morale. The fear of a Corbyn victory outweighs anything any government has felt about its possible successor in the modern era.

The next Conservative leadership election will, as a result, hinge on two questions: why is this happening to us, and how can we stop it? Rees-Mogg’s explanation is simple: Corbyn’s success stems from the fact that he has confidence in his principles, and the Tory problem is that they don’t. Or, as Rees-Mogg himself put it at the 2017 Conservative party conference, the trouble started in 2005, when the Tories looked back at three election defeats and decided “the answer is to be a bit more Blairite”.

One can, from a Conservative perspective, see why this thesis appeals: the polarisation of British politics flows not from any policy decision taken by Conservatives, but a failure to trumpet old school Toryism more loudly. It’s an analysis not altogether removed from Corbyn’s own reading. And who better to sell it than Rees-Mogg, who is Corbyn’s equal and opposite: certain of what he thinks, polite, possessing the appearance of authenticity, if not, perhaps, the reality.

The truth is that the success of both politicians is part of an old story: one party acts, the other reacts. Blair reacted to the success of Thatcherism by appropriating much of it. Cameron reacted to Blair’s success by borrowing from him. Labour activists rebelled against Cameron’s cuts by electing Corbyn. Now, the success of Corbyn in 2017 means that the Conservative activists feel emboldened to disregard the old rules about how to win elections, hoping that their own Corbyn of the right might similarly lead them to an improbable triumph.