Welcome to the 3rd of September 2019, which as it happens is the 80th anniversary of Britain and France declaring war on Nazi Germany, but also seems certain to be remembered in its own right as one of the most important days in modern British political history, perhaps on a par with 28th March 1979 (when the Callaghan government was toppled in a no confidence vote), or 22nd November 1990 (when Margaret Thatcher was forced to resign). What isn't yet clear is exactly how today will be important, but then if we knew what was going to happen in advance, it wouldn't be such a historical crossroads.
It's possible, but unlikely, that the government's threats and browbeating may pay off, and that the Tory rebellion will be minimised to such an extent that a No Deal Brexit becomes virtually inevitable by the end of the day. There would still be the opportunity for Jeremy Corbyn to table a motion of no confidence later in the week, but there's no reason to think that would succeed where the legislative path failed.
On the other hand, if the rebels succeed today, a pre-Brexit general election on 14th October will be on the cards, although not before another putting to the test of Mike Smithson's theory that the Fixed Term Parliaments Act makes early elections practically impossible. If he's proved wrong about that twice in the space of two years, I'll try very hard not to laugh.
Given that we don't know who would win a snap election, it's very difficult to assess the significance of one being called. I'm unconvinced by the polls showing a handsome Tory lead - 30% of the vote is not usually a winning position, and it's only enough for a lead at the moment because of the strange way in which the opposition vote is split. The electorate is more volatile than ever, and there'll be plenty of time during the campaign for the Remain vote to coalesce in a much more effective way. In normal circumstances tactical voting websites have only a minimal effect, but I suspect this time a large fraction of the population will have one question on their minds: how do I cast my vote in this constituency to prevent No Deal? Everything will be up for grabs once minds start to focus.
Only one thing seems reasonably sure: this is the day the Tory/DUP majority in the Commons will finally be wiped out. If the government are true to their word, a large number of Tory MPs will lose the whip today, irrespective of whether the rebellion is large enough to actually win the vote. Boris Johnson's democratic authority for holding the office he does, even over the few weeks needed to hold a general election, will instantly go from being tenuous to non-existent.