The One Nation caucus of self-style moderate Conservative MPs held its second round of leadership hustings this evening. Attempting to beat the pace set by Boris Johnson last night were Michael Gove, Matt Hancock, and Dominic Raab. None managed to pull in as big a crowd as the frontrunner, but their conversations with the comedian Matt Forde did illuminate several new lines of division between the rival camps that could yet change the dynamics of the race.

Dominic Raab won’t rule out proroguing parliament

The former Brexit Secretary was the seventh candidate in all to take to the stage, but became the first to seriously entertaining the prospect of proroguing parliament - a process which would end the current parliamentary session in order to deny MPs any legislative recourse to stop a no-deal exit.

In doing so he went much further than any of the six other candidates, including those, like Johnson and Andrea Leadsom, who have stressed the importance of leaving on 31 October - even if it means doing so without an agreement. Neither, however, is willing to entertain the prospect of prorogation, which many believe would create more problems than it would solve.

It would, in no particular order, politicise the Queen - who would have to adjudicate on whether the request to prorogue had been made in good faith - set a dangerous precedent, raise deeper questions of democratic legitimacy and likely fell the government when Parliament reconvened. (It’s for that last reason Raab’s openness to prorogation is at odds with his pledge not to call a general election, and indeed why every candidate who says they are willing to leave without a deal isn’t being entirely sincere when they rule an election out.)

That Raab was willing to raise a prospect the mainstream of the Conservative Party judges to be completely beyond the pale in such stark terms tells us two things.

The first, as was evident from the long stretches of stony audience silence, is that Raab stands little chance of matching Johnson’s broad and widening appeal among MPs. He even admitted explicitly that he could not deliver everything that his audience stood for. His competitors have striven to give the opposite impression.

That sort of tough line might delight the likes of Andrea Jenkyns - one of the few genuine enthusiasts for Raab in the audience this evening - but it will naturally limit Raab’s ability to speak to the parliamentary selectorate as a whole. Indeed, it’s precisely why many MPs of a One Nation persuasion believe stopping Raab is more important than stopping Johnson.

The second lesson is that there is considerable room for divergence even among those Brexiteer candidates whose pitch is that the UK must leave on 31 October, deal or no deal. With dozens of MPs yet to declare, the shades of commitment to that date that candidates are willing to make could yet have a big impact on numbers.

Michael Gove is up for another Article 50 extension… but his rivals aren’t

One candidate who revealed they did not share that theological attachment to 31 October was Michael Gove. He urged his colleagues not to see the date as a “single totem” and suggested that a short extension of unspecified length might be worth the political pain if it meant completing a renegotiation with the EU.

George Eustice, the former Defra minister and longtime Gove supporter, went even further. He argued that the UK ought not “flounce out” of negotiations “over a couple of months”.

To many Conservative MPs, the prospect of delaying Brexit for a second time is both anathema and electoral kryptonite. It is telling that the only candidates to have made the same admission thus far are also-rans Mark Harper and Rory Stewart, neither of whom are exactly overwhelmed with support.

Candidates fishing in the same pool as MPs as Gove - that is to say Cabinet ministers who have remained loyal to Theresa May - either avoided making a commitment either way, or ruled out an extension entirely. Jeremy Hunt said he would prefer a no-deal outcome to a no Brexit outcome, and his supporters make clear that he classifies a delay as the latter.

Matt Hancock, meanwhile said the alternatives to not passing a deal by October 31 would be extremely damaging. While not quite an outright rejection of an extension in principle, it isn’t as risky as leaning into such a contentious question, as Gove did.

Expect the question of whether 31 October ought to be set in stone to dominate the debate between the Cabinet candidates. It will be asked with increasing urgency after Thursday's Peterborough by-election.

Boris Johnson is still the man to beat

No candidate managed to pack out the room as Johnson did last night. One Gove supporter sniffily dismissed last night's crowd as "stuffed with supporters" when talking up their own man. That might be true, but the ability to command a big crowd at will - or rather, confect one - is an asset no other candidate has.

Raab’s comments on prorogation also underline the extent Johnson has made the running - and defined the debate - on the right flank of the party without harming his appeal among moderates. As his lead grows, tonight’s debates might soon feel very academic.