So there are basically five possible outcomes to the current crisis -
1) May's deal passes
2) No Deal
3) Softer Brexit
4) People's Vote
5) Revocation of Article 50 without a referendum
We can more or less rule out option 5 completely, because the Tory and Labour leaderships are both opposed to revocation. (Admittedly a Labour spokesperson was very careful the other day not to explicitly exclude the possibility, but that was probably just to avoid a backlash from passionate Remainers in the PLP and the party's rank-and-file.) Option 4 isn't totally impossible but looks extremely improbable in the wake of a recent vote in the Commons in which an absolute majority of MPs actively voted against a second referendum. It appears that there are more than enough committed Labour opponents of a referendum to offset any Tory supporters.
So that leaves the first three options as the only credible ones. It's still possible that May's deal will pass next week thanks to a sort of pincer movement of cliff-edges - Remainers might be spooked by the very real possibility of No Deal, while Brexiteer Tories might be spooked by the very real possibility of a softer Brexit. But if the deal doesn't pass at the third and final attempt, which still seems to be the expectation, it's murderously hard to see whether option 2 or option 3 becomes the more likely outcome. Presumably MPs will at last seize control of the parliamentary timetable from the government and will hold a series of indicative votes, in which they might vote for a softer Brexit along the lines proposed by Jeremy Corbyn. But Stephen Bush of the New Statesman, who history has shown has uncanny seer-like powers on matters such as this, seems to think there would only be a 50/50 chance of a Corbyn-type plan passing (in fact reading between the lines I get the impression that he thinks the chances may be a little less than 50/50).
And even if MPs express a preference for a softer Brexit, such a vote would not in the first instance be legally binding, and Theresa May would surely regard it as inconsistent with her government's red lines. She has proved herself to be perfectly capable of completely ignoring the wishes of parliament when they are not binding, and as incumbent Prime Minister there would be various options open to her for frustrating the watering down of Brexit. Which I suppose leads me to conclude that the risk of No Deal should be taken very seriously indeed, even if it's hard to quantify in percentage terms.
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Just a passing thought: hasn't the time come for the SNP and the wider Yes movement to start pointing out to the public that rather a long time has passed since the first independence referendum? Up to now, we've tended to stress the point that a lot of water has passed under the bridge since September 2014, that there has been a material change in circumstances and so on. But we've reached the stage where it's also fair to say that five years is in itself a long period of time, even regardless of the huge change in circumstances. Nobody is pretending that five years constitutes the fabled "generation", but it is the maximum amount of time allowed from one general election to another, it's longer than the entire duration of the First World War, and it's almost as long as the entire duration of the Second World War. If you listened to the unionist parties, you'd think we had a referendum last week.