Before we delve into the more complex features of the coming election campaign, let’s start with a simple proposition. The central question on election night will be: have the Conservatives won enough seats to deliver Brexit?
“Enough” is around 320. Assuming Sinn Fein a) have seven seats again in the 650-member parliament, and b) don’t take their seats, there will be 643 voting MPs. 322 will be needed for an overall majority. With the DUP now firmly against Boris Johnson’s Brexit deal, and a number of pro-Brexit Labour (and ex-Labour) MPs not standing this time, the Tories will need to come very close to an overall majority to achieve their version of Brexit.
Two years ago, the Tories won 318 seats. So as a rule of thumb, if the Tories make net gains on that figure on election night, they will probably be fine; net losses will condemn them to opposition. (If the net change is no more than two or three either way, all bets are off.)
Predicting the outcome is even harder than usual. The opinion pollsters, still smarting from their errors in the last two general elections, disagree on the size of today’s Conservative lead; so none of us can be sure how the parties stand as the campaign starts. Moreover, the electorate is more volatile than ever. The strong, class-based, loyalties of half a century ago have largely vanished. Voters shop around as never before. Even if we knew exactly how much support each party has today, we could not be sure what the numbers will be at the end of the campaign.
Still, we must do the best we can with the data we have. As things stand, and before the campaign gets going, the Conservatives risk losing 20-30 seats: 10-12 to the SNP in Scotland, a similar number to the Liberal Democrats in England, and—though this is less certain—a few Remain-voting London marginals to Labour. To win outright, the Tories need to offset these by gaining enough Leave-voting Labour seats, mainly in the midlands and north.
Add in the electorate’s volatility, and it is possible that the Conservatives will win comfortably—or fall well short of their target. If they do lose seats they could still end up well ahead of Labour. If so, we may have to wait days,…