Never mind the provocative bluster from Boris Johnson’s hollow frontmen and women, there is no disguising the significance of the Tories’ weekend defeat. Of course, many predict rebel Conservatives will now return to the fold, able to support the Johnson deal since the Letwin amendment ensures it cannot be “accidentally” dropped, talked out or stalled before 31 October. But Tory Remainers will soon face another testing option – putting the withdrawal deal to the people in a second Deal v Remain European referendum.

It looks increasingly that this is the only constructive and democratic way out of the Brexit stalemate, and the option’s current traction owes a lot to the growing status of Keir Starmer.

Ian Blackford: Boris Johnson not treating office of PM with any respect

Anti-Brexit protestors march in London.(AP Photo/Matt Dunham)

The shadow Brexit secretary followed an impressive Commons speech on Saturday with a categorical assurance on yesterday’s Andrew Marr Show that Labour will back an amendment calling for a referendum on Johnson’s Brexit deal, perhaps as early as tomorrow. No ifs or buts. No self-defeating subclauses or bizarre contradictions.

Clear, comprehensible and conclusive. Hardly Labour-like at all.

And bold, leaving Britain open to the great risk of a second Leave vote – a result that would then be impossible to sidestep or deny.

A game-changer?

But the plan has just as big an upside – it’s as bold as the disruptive and eye-catching strategy of one Boris Johnson.

Could this be the game-changer that finally unites the opposition around a single Remain plan? Will Jeremy Corbyn back a colleague who’s widely and openly being touted as the next leader of the Labour Party? And will the SNP follow suit?

Strangely enough – even on the fractious left – the answer to both questions could finally be yes.

The stock of Starmer, former director of public prosecutions, has been rising quietly throughout the Brexit debacle but his Commons speech on “super Saturday” was as succinct and punchy as Corbyn contributions are generally “nuanced” and stumbling.

Historian Simon Schama tweeted: “Keir Starmer has actually READ the proposed agreement in crucial detail and thought deeply and forensically about it – and then argues responsibly from that detail. Brilliant, but makes everyone WISH he were leader.”

Such open praise and longing for change at the top would be enough to send a younger rival packing, if Labour had a petty, self-opinionated leader. But while Corbyn may have many faults, personal envy doesn’t seem to be one of them. Indeed Starmer’s success actually reflects very well on the man who appointed him. As one supporter tweeted: “Corbyn runs a team, takes a backseat when needed and lets his star members shine. Other leaders demand the spotlight, refuse to delegate and fail. It’s no coincidence he’s seen out two Tory PMs.”

Jeremy Corbyn

But is the Brexit-leaning Labour leader smart enough to back Starmer instead of overriding him?

A second referendum call has the benefit of being a relatively quick manoeuvre, not requiring a Labour election win, and helpfully separating the party from its own crazy plan to renegotiate Brexit but then campaign against its own new deal in a second referendum. Supporting Johnson’s deal would placate Brexit supporters and the “just get it over with” brigade, while also delighting Remain voters with the possibility that the attached second vote might dump Brexit altogether.

Indeed the only thing wrong with Starmer’s second referendum plan is that it opens Labour up to the accusation of being feart – failing to propose a vote of no confidence and a general election, even though the next EU extension will certainly end the danger of a no-deal Brexit.

So will Corbyn back a confirmatory referendum on Johnson’s deal? He might, if other parties back the move. It’s rumoured high-profile Tories such as Amber Rudd now accept there’s no other way to break the deadlock. Will she and other rebels openly back a second referendum if a suitably neutral backbencher champions the cause? Starmer even hopes to coax the DUP on board. Good luck with that. But what about the most important block of votes – the SNP. Is it ready to play ball?

Backing the wrong horse

Speaking on Sunday Politics Scotland, Ian Blackford wouldn’t commit the SNP to following Labour’s lead and talked instead of another court case or a vote of no confidence. It seems a strangely wooden response to a fluid situation and leaving the SNP in danger of backing the wrong horse tomorrow. Nicola Sturgeon has suggested that the path to a second vote will be rockier than anyone appreciates.

Certainly, if the amendment passes, it’s not clear how a second vote will be organised. Can Johnson really be expected to produce a fair, timeous, workable referendum he doesn’t want to hold? The childish, churlish clutch of letters sent to the EU this weekend shows how grudging he can be. That’s why many MPs believe a “government of national unity” (GNU) is the only way to deliver a second vote that resolves the Brexit process once and for all.

SNP MP Joanna Cherry believes such a scenario is the best chance of winning a Section 30 order – which would allow the Scottish Parliament to hold a legally binding second independence referendum – not just because the SNP would be in a bargaining position but also because democrats from other parties would find it hard to deny the inconsistency in their current second vote positions.

There’s also clear popular support amongst Scottish voters for a pan-UK second vote to end the EU withdrawal deadlock. A new Panelbase poll found that only 26 per cent supported a general election - Nicola Sturgeon’s current stance - while 46 per cent would prefer another referendum. 27 per cent were don’t knows.

Of course, the SNP may worry that a confirmatory referendum on Brexit sets a difficult precedent for indyref2. It might, but we are where we are – perhaps about to find a democratic solution for a stalemate which might otherwise hand the next general election to Johnson on a plate.

It’s also hoped the end of the Union will be more of a “conscious uncoupling” than a Brexit-style bust-up. Talks with opposition MPs in Scotland and London have been progressing quietly, aided by joint working over Brexit. Starting the indyref2 project in a collaborative, non-confrontational way allows the slender hope that constitutional change in Scotland will not be conducted with the high-handedness of the Conservatives’ Brexit.

So all eyes will be on the backbenches tomorrow.

If a well respected figure allows Labour to push for a second vote, and the SNP, Liberal Democrats and some Tory rebels follow suit, Britain’s constitutional logjam could be released far more quickly than anyone imagines.

Lesley Riddoch: SNP must back Labour’s Brexit vote plan