This Thursday's an electoral rarity for the United Kingdom: a moment when, mid-Parliament, absolutely everyone is going to have a vote. Perhaps more than one. We've tried to popularise the idea that this is a truly 'MegaThursday', but for some reason that doesn't seem to have caught on, so we'll limit ourselves to just talking about a truly Super Thursday - the biggest test of public opinion, and the parties' relative strength, between now and May 2020. Forgive us if we don't delve into the electoral politics of Northern Ireland, or the Police and Crime Commissioner elections (where many Independents make things livelier than they might otherwise be), because - fascinating as those contests are - we're interested here in the Great Britain parties' relative prospects.
We've looked before at the benchmarks by which to judge Labour's performance, but how might the night as a whole shape up? Let's look at the contests in turn, in no particular order.
Scotland. Here the Scottish National Party is almost certainly going to form another majority government. We take that so much for granted these days, accepting the yellow tide across Scotland's electoral map without a thought or a comment, that it's worth pausing for a moment and considering just how astonishing that is. The SNP can now scoop up (just about) half the vote. Their priorities and questions dominate Scotland's political and even cultural landscape. They are able to reach the majority finishing line at Holyrood (above) without breaking much of a sweat - in a proportional system deliberately and explicitly designed to prevent that outcome. That won't always be the case, of course (the eventual electoral fate and crisis of the Parti Québécois in Canada shows that clearly enough) - but for now, and probably for some years to come, there's little point in the other parties shouting at them. They're just locked in a fight for the crumbs from the SNP's table. Here the only question is: can the Conservatives come second? The popularity of their tough and impressive leader, Ruth Davidson, as well as unionist voters' antipathy to a Labour leadership that seems a little ambivalent about the independence question, says yes: cultural antipathy to the Conservatives, and the stigma of actually voting for them, says no. We expect Labour to scrape into second: if they do not, the Conservatives will be able to point to a modest and gradual, but real, recovery in Scotland, while Scottish Labour will have had another of their miserable, miserable nights. There are probably many more to come.
Our call: An SNP majority of about the same size as now; Labour to come second, but lose all, or almost all, of their constituency seats. An SNP majority government in Edinburgh.
Wales. Here things are even more uncertain. Labour seem pretty certain to lead the next government in Cardiff Bay, but everything else is a little, well... up in the air, especially as Labour seem at the same time quite likely to fall to their lowest ever share of the vote for these contests. Two trends in the fight for second, third and fourth are notable. During the campaign, recent years' relative improvement in Conservative fortunes in Wales seems to have stalled - little surprise, perhaps, given the Government's uncertain handling of the Tata steelworks imbroglio - while Plaid Cymru, the Welsh Nationalists, do seem to have wrapped up the fight to come second and form the official Opposition. Behind them, a surge of support for the United Kingdom Independence Party exactly where you would expect to find it - among older, less educated and more excluded voters in South Wales - is on the way. UKIP seem poised to win seven or eight seats. That will change the electoral geography of Wales for the next few years, and perhaps make governing there much harder. It may force Labour, Plaid Cymru and any Liberal Democrats that remain in the Senedd closer together so as to meet this threat from the populist Right - though we wouldn't count on it. One other thing to note here: Welsh polls usually come from just one firm, which over-rated Labour's chances in the last Welsh election by about five points on the constituency vote, and seven points on the regional list. If that happens again, Labour will be in big, big trouble, and may even be struggling to cling to power at all. The company in question (YouGov) have done everything they can to change their polling methodology since the debacle of the last General Election, but have they done enough to factor in widespread Labour apathy and the attractions of a UKIP vote in South Wales - at a time when Labour have definitely gone backwards on the last time these seats were fought? If they haven't, Labour is set for a miserable night indeed.
Our call: Labour to do badly on vote share, but to hang on to most of their seats, returning 27-28 AMs; Plaid to come second, with the Conservatives perhaps disappointing on the night and UKIP securing 6-8 AMs. A Labour minority administration in Cardiff Bay.
English local government. Here things are even more complex, and you should ignore any temptation to tell big old stories just as soon as the polls are closed. It is true that Labour should be doing well here, six years into a not-particularly-popular government austerity government; on a historic basis, they should be winning hundreds of seats and growing their vote share. Anything below a high-30s finish in terms of National Equivalent Share of the vote is a very, very clear indicator that they are about to lose the next General Election (if you needed any other hints in that direction). Though this number may have come down a bit given the rise of UKIP, Labour finishing behind the Conservatives in vote share, as they are forecast to do, would be just one more signal that everything the polls and local by-elections are telling us is right: that Labour are utterly becalmed, perhaps even sinking a bit since last year. On the other hand, Labour did well in just these elections when they were last fought on a comparable basis, in 2012, and UKIP are doubling their candidate count: this seems likely to exaggerate any seat loss (or dramatically shrink any gain) that we would have been expecting. In places such as Thurrock and Harlow, in Essex - both Parliamentary seats Labour held very recently - UKIP's increased presence since 2012, when many still regarded as them as something of a fringe party, may have a very profound impact indeed. They will take seats themselves; but they may also hand seats to the Conservatives by eroding the traditional Labour vote in many wards. It'll be a confusing picture. Labour will probably do well in some urban areas, but perhaps poorly across the South of England. The electoral geography of all this is important: keep an eye out for where the parties actually do well, rather than just the raw seats total. Away from the Labour-UKIP dogfight, the Liberal Democrats will probably continue their relatively pleasing progress in local by-elections with a small push forward - they are thick on the ground where they have recently lost Parliamentary seats, and seem up for a fight. The Conservatives will probably have a very good night given their recent travails, splits and rows - an amazing achievement, really, when you keep in mind how bad things have seemed for them at times in recent weeks.
Our call: Labour may well lose seats, but perhaps not as many as our statistical models suggest; very little precision is possible here. Tribal loyalty and voters' desire to re-elect Labour councils trying to protect services may shelter the party from its constant tragi-comic blundering at national level. UKIP may seem to have a really great night, though that may have more to do with putting up more candidates than an increase in their vote share where they do contest council wards.
Our call: Sadiq Khan will almost certainly be the new Mayor, and he might win quite easily - not by the landslide you might expect from some polls, but at a canter nonetheless. If he doesn't, you can expect full-on hand-to-hand fighting within the Labour Party to start immediately. It's been lucky for them that Mr Goldsmith has fought such a poor campaign, though Labour would probably have won narrowly anyway.
So it's set to be a good night for UKIP, a so-so night for the Liberal Democrats, an unexpectedly not-as-bad-as-it-might-have been result for the Conservatives, and a disappointing (though not we think cataclysmic) result for Labour, who will at least be consoled by victory in London. Or, just maybe: none of the above. We'll soon know - and then we'll be able to test all those numbers we've been harvesting so far this Parliament, and tell you exactly why the actual results differed from these projections. Print these predictions out. Hold us to them. Some of these battles may look a bit esoteric or a little dry, but what they tell us about the British people and what they think certainly are not. At least one thing is clear, among the statistical fog: for the moment at least, British politics is never, never dull.