When to go to bed tonight

For UK readers

I did this analysis for my own benefit, but there may be others who need to be wide awake on Friday who might find this information useful. But if you retire early on the basis of this post and find out things are very different when you wake up, I take no responsibility! My macro you can believe in; with this stuff I’m an amateur.

Unless current polls are wildly wrong, there are only two likely results: the continuation of the current coalition (except in the unlikely event that the LibDem party rejects its leadership), or a Labour government with SNP support. There will be plenty of interesting side-issues going on as well (how dominant will the SNP be, how many seats will UKIP win), but the main result will depend on the Labour/Conservative marginals which Labour must win to form a government, and that is what I focus on here.

10pm

One obvious strategy is to switch the TV off when the exit polls are announced after the polls close. They will of course tell us a lot, but they are not nearly as infallible as you might at first think - in fact the information they provide has to be processed in various ways, as these two studies spell out (HT Chris Giles). Those producing the poll know they could easily be wrong.

11pm-1am

No important marginals are expected to declare before 1pm, but the first results will be an additional indicator of the national swing. (Remember the Conservative's actual vote share is usually greater than in the final opinion polls: the 'shy Tory' effect.) To give you an idea of how close it will be, both YouGov and Elections etc suggest that a 3% point Conservative lead (e.g. 35 to 32) will produce a Cameron victory (but probably depending on the DUP), while Election forecasts suggest a 2% point Conservative lead gives a final Lab+SNP seat total of just over 315, which should be enough for a Miliband minority government with SNP and minor party support. 

However, like the exit polls, these early indications may be misleading. A great deal depends on the extent of tactical voting, and in particular about many UKIP supporters are prepared to vote for another party in a marginal seat. 

1am-3am

Many Labour/Conservative marginals are predicted to declare around 3am, but there are five exceptions. Probably the first is Nuneton, expected at 1am. This should be a Labour gain - if it is not, things are looking very good for the Conservatives. If Labour win this then the next critical seat could be Northampton North at about 2am - a real knife edge seat. If Labour win this easily things are looking good for them, but a close loss might not be fatal. (Look at what happens to the UKIP vote: if the Conservatives win with a UKIP vote share of around 10% or less, that is a good sign for the Conservatives.)

Two other Lab/Con marginals that might declare before 3am are Chester and Warrington South. Chester should be a Labour gain, but Warrington South is another knife edge seat. Both LibDem and UKIP support is significant here (15% and 10% respectively) so if either breaks in one direction this could decide the result. Cleethorpes may also declare before 3am: a recent Ashcroft poll gave the Conservatives a 2 point lead here, so a Labour gain would be a great result for them.

If Labour lose four or more of these five, I think you can almost certainly go to bed at this stage knowing that Cameron will remain Prime Minister. If Labour wins four or five, Miliband is looking good, but to be sure you need to stay up a bit longer. Another interesting seat that may come in around 2am is Rutherglen & Hamilton West - if Labour with a good local MP lose this to the SNP, they will probably lose nearly all their Scottish seats.

3am

Around 3am a whole clutch of seats are due to declare:

Amber Valley: probable Lab gain, but with a potentially large UKIP (>10%) vote

Bedford: another likely Lab gain, but with significant (around 12%) UKIP and LibDem support

Brent Central: almost certain Lab gain, but if close a worry for Labour’s potential London gains

Bristol West: very likely Labour gain if Ashcroft poll is right - outside Green chance

Bury North: likely Lab gain, but again potentially large (13%) UKIP support

Carlisle: as above

Croydon Central: a very significant London seat. This was thought to be a potential Lab gain, but a very recent Ashcroft poll gave this to the Cons.

Erewash: as Bury North

Hastings: should be a Labour gain, but UKIP could spoil things here

Hornsey: potential Labour gain from LibDems, but will Cons vote tactically?

Peterborough: If Labour wins this (as a recent Ashcroft poll suggested) this will be a good result for them. UKIP could again be crucial.

Stockton S: Another real marginal, that a recent Ashcroft poll gave to Labour

If Labour gain less than eight of these seats, Cameron is probably going to be the next PM. If they gain them all, Miliband probably will be. Anything in between, and you will have to wait another hour before things become clearer. Or with 8 or 9 key marginals not expected to declare until around 5pm, you could just decide to call it a night and find out in the morning!