The key questions for the coming general election

1. What are the real winning posts?

For an outright majority, the winning party needs 326 MPs. But to decide who will be prime minister in six weeks’ time, the answers are different for the two main parties. What matters is whether there is a pro or anti-Conservative majority in the new House of Commons.

The Tories are pretty much on their own — their only possible (but not certain) allies are Northern Ireland’s Democratic Unionists. To have any chance of staying in office, Rishi Sunak will need at least 315 Tory MPs (this assumes that Sinn Fein’s MPs continue to boycott parliament).

Robert Buckland, the former lord chancellor, is defending a majority of 5,670 in Swindon South. If he holds the seat for the Conservatives, Sunak has a good chance of remaining in office. If Labour’s Heidi Alexander achieves the seven-point swing she needs to win the seat, Sunak’s prospects will be bleak.

Labour’s winning post is different. It needs only 270 MPs for there to be an anti-Conservative majority and for Keir Starmer to be virtually certain to move into Downing Street. The number may even be slightly smaller: it will depend on how many other anti-Conservative MPs are elected — Liberal Democrats, Scottish National Party, Plaid Cymru, Green and probably two or three from Northern Ireland.

However, such a hung parliament would be unlikely to last. For a majority large enough to survive a full five-year parliament, Starmer will need at least 340 Labour MPs.

The fate of the net-zero minister Justin Tomlinson, Buckland’s neighbour in North Swindon, could determine this. He is defending a majority of 13,250. Labour’s Will Stone needs a 14 per cent swing to win the seat and help Starmer reach his target. To hold on to either, let alone both Swindon seats — alongside dozens of others — the Conservatives need to revive the coalition of 14 million voters that gave Boris Johnson his big majority last time.

According to YouGov’s latest poll, two million of them would now back Reform, while more than three million say “don’t know” or “won’t vote”. How many of those five-million-plus can Sunak win back? They hold the key to his hopes of preventing a Labour landslide, let alone remaining prime minister.

2. Will the Tories suffer a backlash in the red wall?

In 2017, and even more in 2019, the Conservatives invaded Labour’s traditional heartlands with great success. Their slogan, “Get Brexit done”, attracted people who had never voted Tory before. The evidence from polls and this month’s local elections is that many Leave voters have swung back to Labour. Precisely because of the geography of Johnson’s victory, many of these voters live in seats that Labour needs to win.

Grimsby went Conservative in 2019 for the first time since 1935, after 70 per cent voted Leave in 2016. Lia Nici is defending a majority of almost 10,000 in the new seat of Great Grimsby and Cleethorpes. It ranks 106th in the list of Tory seats that Labour hopes to win, but Nici is highly vulnerable unless Sunak can regain the support of Leave voters who have drifted away.

3. Will tactical voting give Labour and the Liberal Democrats bonus seats?

In 1997, many Lib Dem supporters in Conservative-Labour marginals backed Tony Blair to become prime minister, while many Labour supporters backed Paddy Ashdown’s Lib Dems in his target seats. Labour would have won a big victory anyway, but detailed analysis of voting patterns suggests that tactical voting gave Labour an extra 20 seats, and the Lib Dems ten.

In 2019, Jeremy Corbyn and Jo Swinson had no such effect. The latest signs are that tactical voting is back. By-elections and this month’s local elections confirm that many anti-Tory voters are happy to back whichever party is best able to beat the Tories locally. Two of the Conservatives’ biggest beasts are vulnerable: Jeremy Hunt in Godalming and Ash and Jacob Rees-Mogg in North East Somerset and Hanham. Hunt is defending a majority of 10,720 over the Lib Dems, while Labour hope to overturn Rees-Mogg’s majority of 16,389. In both seats, tactical voting could cost the Tories seats they might otherwise hold.

4. Can Labour overtake the SNP in Scotland?

On the face of it, this seems implausible. Last time, the SNP won 48 seats while Labour came fourth with just one. But Labour has been climbing in the polls, and in October won a remarkable victory in a by-election in Rutherglen, where Michael Shanks surged past the SNP on a 20 per cent swing. For Labour to come top in Scotland, it needs to gain seats such as Glenrothes and Mid Fife, which the SNP won last time with a majority of 9,352.

The Lib Dems have a keen interest in the fate of the SNP. In 2015, when the Lib Dems lost 49 of the 57 seats across Britain they had won in 2010, they were reduced to fourth place at Westminster. They hope to regain third place this time, and with it more chances to have their voice heard in parliament and, by  convention, on radio and television. A weak SNP performance in Scotland, combined with tactical voting in England and Wales, would help Ed Davey achieve that objective.

Note: All the majorities above relate to Britain’s new parliamentary boundaries. They are estimates by Colin Rallings and Michael Thrasher of the votes in 2019 in each seat, had they been fought on the new boundaries.

This analysis was first published by the Sunday Times