#GE2015 Forecast from Elections ETC

It’s a tossup! Our model now gives Labour and the Tories each a 50% chance of winning the most seats, and our central forecast is for them each to win 281 – leaving them both 42 seats short of a majority.
That represents a very small shift towards Labour since last week’s forecast, which had the Tories slight (52%-48%) favourites to win the most seats and a central forecast of 282 Conservative MPs to 279 Labour ones.
That’s not because the polling’s moved towards Labour (it hasn’t: our average still them on 33% to the Tories’ 32%, for the sixth week in a row), but because another week has gone by without the Tories making the gains history suggests they should.
Before getting too excited about the possibility of both parties winning the same number of seats, it’s worth remembering that, although it’s our central forecast, that specific outcome (like any specific combination of MPs) is not very likely. Note that our confidence intervals are still pretty large: roughly ±50 seats for both the Conservatives and Labour.
More important is the broad picture of this election, which remains unchanged since last we launched our new model a month ago:
The Tories are likely to win the most votes (with a 69% chance), but not by much (central forecast: Con 33.7%, Lab 31.4%). So it’s 50-50 as to which party wins the most seats, and we’re likely to end up with a hung parliament (85% chance) with the two largest parties pretty finely-balanced.
Labour are more likely to be able to form a government, though, largely due to the presence of a number of SNP MPs (41 in our central forecast). Our model suggests a 58% chance of a Labour-led alliance commanding a majority, an 18% of a Conservative-led one doing so, and a 24% chance that either could, depending on whom the Lib Dems supported.

Date of forecast: 13 February 2015
Days till the election: 83
Inputted current average poll shares
Con: 32%
Lab: 33%
LD: 8%
UKIP: 15%
Others: 12%
Forecast GB Vote Shares (with 95% Prediction Intervals)
Con: 33.7% (29% – 38%)
Lab: 31.4% (27% – 36%)
LD: 10.2% (6% – 15%)
UKIP: 13.7% (9% – 18%)
Others: 11.0% (9% – 13%)
Forecast Scotland Vote Shares (with 95% Prediction Intervals)
SNP: 44% (40% – 48%)
Labour: 30% (26% – 34%)
Forecast GB Seats (with 95% Prediction Intervals)
Con: 281 (234 – 333)
Lab: 281 (231 – 324)
LD: 23 (13 – 36)
SNP: 41 (28 – 51)
PC: 3
UKIP: 3
Grn: 1
(May not sum to 632 due to rounding of sums of probabilities. Prediction intervals not yet available for UKIP, PC and Grn.)
Central forecast: Con largest party, but short of a majority by 41
(Criterion for majority now changed to 323 not 326, assuming Sinn Fein win 5 seats and do not take them.)
Probabilities of key outcomes
Con largest: 50%
Lab largest: 50%
Hung Parliament: 85%
… with Con largest: 41%
… with Lab largest: 44%
Probabilities of predicted government outcomes:
(See here for explanations and assumptions)
Con majority: 9%
Con+NDown: 0%
Con+ND+DUP: 5%
Con+ND+LD: 9%
… with Con+ND+DUP also possible: 5%
… without Con+ND+DUP also possible: 3%
Con+ND+DUP+UKIP: 0%
Lab majority: 5%
Left (Lab+SDLP+PC+Grn): 4%
Left+LD: 25%
… with LD as kingmakers: 0%
… without LD as kingmakers: 25%
Left+SNP: 47%
… with Left+LD also possible: 25%
… without Left+LD possible: 22%
Left+SNP+LD: 25%
… with LD as kingmakers: 24%
… without LD as kingmakers: 1%
LD kingmakers: 24%
With a choice between Con+ND+DUP(+UKIP)+LD or
…Lab+SDLP+PC+Grn+LD: 0%
…Lab+SDLP+PC+Grn+SNP+LD: 24%
(Probabilities may not sum due to rounding)