If you don’t like the sound of teeth being gritted, never ask a Labour MP how they feel about cooperation with the Liberal Democrats. “I know it makes sense,” one member of the shadow cabinet recently gnashed their molars to me. “But it really sticks in the craw.” That is an effusion of affection compared with their history of bitter animosity. They weren’t speaking when Jeremy Corbyn led Labour. Corbynites treated the Lib Dems as indistinguishable from Tories – or, worse, Blairites – and Lib Dems regarded Mr Corbyn with horror. During the Cameron-Clegg coalition years, Labour people were often much more vicious about the Lib Dems for participating in that government than they were about the Tories who dominated it. The key people on both sides have put all that behind them. Gradually, Sir Keir Starmer and Sir Ed Davey have been edging closer, driven towards collaboration by a mutual hunger to evict the Conservatives. Both have come to understand that each needs the other to do well. The Lib Dems can hurt the Tories, as they demonstrated in the local elections, but know it will also require a strong Labour showing at the next general election to be sure of dislodging the Conservatives from office. Labour’s leadership will never acknowledge anxieties that they can’t win on their own, but everyone can see the immense size of the electoral mountain. It is generally reckoned that Labour needs a swing to them from the Tories of around 10 points to achieve a Commons majority of just one. That scale of swing has happened in British politics, but it is an event as rare as Boris Johnson being found telling the truth. Many senior Labour people privately think that a more realistic goal is a hung parliament. The Lib Dems can help make that happen by unseating Tory MPs in places where Labour can’t. I first reported to you last autumn that both parties were warming to an informal pact in which they don’t waste precious resources attacking each other and concentrate their energies where each is best placed to beat the Conservatives. The fruits of that are now becoming apparent to all. A low-key Labour presence in the North Shropshire byelection helped direct voters to the Lib Dems as the instrument to remove the Tories from what was previously a very safe blue seat. Something similar happened in Chesham and Amersham. A tightly targeted Lib Dem effort in the Batley and Spen byelection, where they focused on picking off Tory support, helped Labour defend that seat against a Conservative challenge. We now have two further byelections to look forward to – though not, I suppose, if you are a Tory. Both contests have been triggered by the disgrace of Conservative MPs. Sir Keir’s party will concentrate on Wakefield, a Yorkshire seat that Labour held before the 2019 election. The Lib Dems are mobilising their byelection shock troops into the West Country where Tiverton and Honiton is up for grabs. They are helping each other in another way. When Mr Corbyn was Labour’s leader, he was a disaster not just for his own party but as much so for the Lib Dems. Fright at the thought of letting him into Number 10 made many middle ground voters hold their noses and stick with the Tories. To this kind of voter, Sir Keir as prime minister is a much less scary proposition and thus de-risks choosing the Lib Dems. This is borne out by conversations with Conservative MPs representing affluent areas of southern England where the principal challenge comes from Sir Ed’s party. One of these Tory MPs, who represents a constituency held by the Lib Dems between 1997 and 2010, says “a less alarming Labour leader” makes it much more likely he will lose his seat. The live question is where and how far collaboration should go from here. Can the unspoken pact for byelections be developed into a deeper cooperation that reaps dividends at the next general election? Some advocate a formal “progressive alliance” in which Labour stands down its candidates in some places and the Lib Dems vacate the field in others. The Greens could also be a component of a non-compete agreement. I’d say the chances of that kind of deal are somewhere between zero and zip. Both leaderships think this would be a recipe for endless ugly rows accompanied by furious rebellions by local activists unwilling to take instructions from above about seat deals. Rather than look united in their resolve to remove the Tories, they’d be more likely to become destructively quarrelsome. There is something else that strategists in both parties fear. Some voters might warm to an explicit link-up, but others could recoil at a formal pact, which the Tories would depict as a grubby stitch-up. This would be hypocritical of the Tories. They didn’t complain when the Brexit party withdrew candidates in more than 300 seats at the last election to the great benefit of the Conservatives. Hypocrisy be damned, the Tories will denounce Lab-Lib cooperation anyway, not least because it is rattling them. Rather than a formal pact, the more fruitful way forward is a wider informal alliance anchored in principles and what is best for the country. Though they don’t agree on everything, there’s very little about which they violently disagree. Concentrating their resources where each has the best chance of success makes all the more sense because neither party is flush with cash. The vast majority of the Lib Dems’ target seats are Conservative-held. For Labour, the next election will be decided not on the few scraps of turf where they compete with the Lib Dems but on the sweep of battlegrounds where they are fighting Tories or nationalists. It is instructive to look at what happened in the run-up to the 1997 general election when there was a very well-organised Lab-Lib pincer movement against an entrenched rightwing government. A new report, 1997: Then and Now, highlights the extent and the effectiveness of the collaboration. Tony Blair, leading Labour, and Paddy Ashdown, his Lib Dem counterpart, generally avoided criticising each other and made a virtue of what they had in common while coordinating their attacks on the Tories on occasions such as prime minister’s questions. The report’s author, Duncan Brack, a historian and former Lib Dem adviser, reminds us that they commissioned joint work on constitutional issues. They also shared information on target seats and sent strong signals to encourage tactical voting. “The report shows we have done it before – and we can do it again, better,” says Neal Lawson, director of the campaign group Compass. The result in 1997 more than doubled the number of Lib Dem MPs to 46 and delivered a landslide majority to Labour. A hung parliament looks a likelier outcome of the next national contest. Both the local elections and the current polls suggest one. A shrewd Tory remarks: “Of the possible election outcomes, I think a hung parliament is the most under-priced.” That alarms the Conservatives, because they are so repellent to all the other parties. Their only possible partner in a hung parliament would be the DUP, who might very well balk after what has happened to them since Brexit. The DUP are, anyway, of help to the Tories only if they fall a little short of a majority. “Labour doesn’t have to win for us to be out of power,” observes one nervous Tory MP. “We just have to lose.” The Conservative plan is to try to flip the prospect of a hung parliament from a menace to them into a threat to their opponents. They are already talking about repeating David Cameron’s tactics during the 2015 election, when a hung parliament was widely regarded as a likely outcome. The then Tory leader mongered scares about “a coalition of chaos” involving Labour, the Lib Dems and the SNP. The most potent piece of Tory propaganda featured a miniature Ed Miliband imprisoned in the pocket of a giant Alex Salmond. We’ve since had seven years of Conservative chaos, but that won’t stop the Tories reprising this kind of campaign. It was brutally effective in 2015, not least because neither Labour nor the Lib Dems saw the assault coming. By the time the Tories were doing their ruthless worst to petrify swing voters, it was too late to construct robust defences, both parties suffered at the ballot box and the Conservatives won – again. So another thing Sir Keir and Sir Ed need to be thinking about, and it would be best to start now, is how to prevent that horrible history from being repeated at the next general election.