Could tactical voting oust the Conservatives at the next general election?

The potential flaw is that voters are not a bloc that can be moved from one column to another, writes Andrew Grice

It seems unlikely that there will be any formal pact between Labour and the Lib Dems (Getty/PA)

Some Conservatives argued that the North Shropshire by-election was a bad result for Labour because the Liberal Democrats overtook the party from third place in 2019 to win the seat. Yet some senior Labour figures believe it was a very good result for them.

For years, there has been talk of an anti-Tory progressive alliance involving Labour, the Lib Dems and the Greens. Some local pacts, under which candidates stood aside for the party with the best chance of winning, were agreed at the 2017 election, but the Greens got their fingers burnt when other parties did not reciprocate.

The potential flaw is that voters are not a bloc that can be moved from one column to another. Some “soft” Tory voters might lend their support to the Lib Dems, but not to Labour. But voters now seem to be doing it by themselves, in a DIY democracy made necessary by the first-past-the-post system. The Labour vote collapsed in Chesham and Amersham, as well as in North Shropshire, to help the Lib Dems claim famous victories. In a variation on the theme, the Lib Dems campaigned hard in a few areas in Batley and Spen where Tory support was soft, helping Labour over the line.

Although relations between Labour and the Lib Dems have improved since Jeremy Corbyn’s departure, there is no formal agreement between Keir Starmer and Ed Davey. The pact is unspoken, but real – indeed, Starmer has hinted at it in recent remarks – and some Tories now sense danger. The Lib Dems came second to the Tories in 80 seats in 2019, mostly in the “blue wall” in the south of England. Twenty-three would fall to them on a 10 per cent swing.

Some campaign groups want the opposition parties to make their partnership official. “What is given in by-elections is often taken away in generals unless progressive parties learn to work more effectively together,” said Neal Lawson, director of Compass.

Labour would need a 10 per cent uniform swing to win an overall majority, but could be the largest party on a 4 per cent swing. The Tories will doubtless warn voters against a “coalition of losers” – a recognition that they could be the largest party in a hung parliament but, with no likely partners, powerless to stop Sir Keir heading a minority government with the tacit support of the Lib Dems and the Scottish National Party. The prospect will be harder to attack if there is no formal Lib-Lab deal; that is one reason why there won’t be.

“It worked in 1997 and it can work next time,” one Starmer ally told me, referring to the informal pact between Tony Blair and Paddy Ashdown to soft-pedal in about 100 seats where the other party stood a chance of beating the Tories. In the event, Mr Blair did not need the Lib Dems in order to win his landslide. Sir Keir, requiring a swing bigger than that secured by Mr Blair if he is to win an overall majority, will need them in 2024.