How well does Labour need to do in the Corby by-election?

The party needs to win a majority of at least 12 per cent to match its current national poll lead.

Barring some dramatic upset, Labour will win today's Corby by-election (triggered by the resignation of Louise Mensch), gaining a seat from the Conservatives for the first time in this parliament. But winning alone isn't enough. A slender victory would prompt fears that the party still isn't where it needs to be if it's to stand a chance of winning the next general election. Thus, while Labour requires a swing (the rise in one party's vote added to the fall in another's and divided by two) of just two per cent to overturn the Tories' majority of 1,951, it needs a swing of at least five per cent to put it on course to win a national majority in 2015 and a swing of eight per cent to justify its average opinion poll lead of nine points. The latter would see it take the seat with a majority of around 12 per cent. 

To win Corby: Labour needs a swing of two per cent.

To win a majority in 2015: Labour needs a swing of five per cent to put it on course to win a majority at the next general election.

To match its national poll lead: Labour needs a swing of eight per cent to match its average national poll lead of nine points.

Polling by Lord Ashcroft in the constituency has suggested that Labour will easily exceed this benchmark. His final survey gave the party a lead of 22 points (with Labour on 54 per cent and the Tories on 32 per cent) and showed a swing of 12.5 per cent from the Tories to Labour.

Labour, naturally, has downplayed Ashcroft's findings, insisting that Corby will be "a very tough fight" in an attempt to ensure its supporters turn out. Ed Miliband reminded party workers last week that the party thought it had won in 1992 but ended up losing to the Tories by 342 votes. While history isn't likely to repeat itself today, anything less than a resounding victory in this mid-term electoral test will force Labour to ask why it isn't doing better.

Update: As the commenter below points out, there are two other by-elections today, in Manchester Central and Cardiff South and Penarth. Labour currently holds both seats by majorities of 10,430 and 4,709 respectively and is expected to retain them.

In addition, the first ever police and crime commissioner elections are taking place in 41 police authority areas in England and Wales. You can read my guide to the elections here.

Ed Miliband is hoping Labour can win a seat off the Conservatives for the first time since he became leader. Photograph: Getty Images.

George Eaton is political editor of the New Statesman.

Photo: Getty
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Who will win the Copeland by-election?

Labour face a tricky task in holding onto the seat. 

What’s the Copeland by-election about? That’s the question that will decide who wins it.

The Conservatives want it to be about the nuclear industry, which is the seat’s biggest employer, and Jeremy Corbyn’s long history of opposition to nuclear power.

Labour want it to be about the difficulties of the NHS in Cumbria in general and the future of West Cumberland Hospital in particular.

Who’s winning? Neither party is confident of victory but both sides think it will be close. That Theresa May has visited is a sign of the confidence in Conservative headquarters that, win or lose, Labour will not increase its majority from the six-point lead it held over the Conservatives in May 2015. (It’s always more instructive to talk about vote share rather than raw numbers, in by-elections in particular.)

But her visit may have been counterproductive. Yes, she is the most popular politician in Britain according to all the polls, but in visiting she has added fuel to the fire of Labour’s message that the Conservatives are keeping an anxious eye on the outcome.

Labour strategists feared that “the oxygen” would come out of the campaign if May used her visit to offer a guarantee about West Cumberland Hospital. Instead, she refused to answer, merely hyping up the issue further.

The party is nervous that opposition to Corbyn is going to supress turnout among their voters, but on the Conservative side, there is considerable irritation that May’s visit has made their task harder, too.

Voters know the difference between a by-election and a general election and my hunch is that people will get they can have a free hit on the health question without risking the future of the nuclear factory. That Corbyn has U-Turned on nuclear power only helps.

I said last week that if I knew what the local paper would look like between now and then I would be able to call the outcome. Today the West Cumbria News & Star leads with Downing Street’s refusal to answer questions about West Cumberland Hospital. All the signs favour Labour. 

Stephen Bush is special correspondent at the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to British politics.