Among the many things that went wrong in 2017 was a serious error in the selection of target seats, and therefore the allocation of campaign resources and activists. Starting with insufficient and somewhat obsolete data, the Conservative Party struggled to select its targets in the early stages of a campaign for which it wasn’t adequately prepared. Desperate to inform its decision-making, it then updated its selections after a few weeks, based on polling and local election data – only for that information to be rendered incorrect by events, not least the manifesto problems and the growing ‘weak and wobbly’ narrative about the Prime Minister.

The trouble was, the damage was done before the error was realised. They started ambitiously – even targeting a few rare seats with Labour majorities as large as 8,000 – and then the early poll leads and encouraging locals led the operation to get greedy. They switched resources out of defence seats and tight marginals, and into stretch targets, with ruinous effect.

Here is my report after the election:

‘…as the results came in, numerous experienced campaigners in Tory seats with large majorities realised to their horror that while they had been travelling often long distances to give mutual aid to supposed target seats where Labour won convincingly, Tory-held seats far closer to them had been lost. In one instance, a well-resourced association saw the Labour majority in their allotted target seat increase, while a Conservative seat which they drove through regularly to get to the target was lost.

This mismatch got worse as time went on, too. Positive early canvassing returns (pre-manifesto) and the encouraging local election results led CCHQ’s strategists to start not only treating Tory-held marginals as safe, but to divert resources away from the more marginal Labour-held target seats and towards target seats further down the list, ie those with bigger majorities. A candidate in what was supposed to be a top target – Leave-voting, and narrowly held by Labour in 2015 – tells me that:

“CCHQ’s eyes were definitely bigger than their belly. The limited resource we had in [our area] was originally due to be directed to us. That would have already been a stretch, but once canvass returns came in we lost it all together as 5-8,000 majorities were targeted instead. It left us very exposed.”

The moral of the story is that it’s better to stay focused on getting the essentials right than neglect them because you’re carried away with fantasies of a landslide. It’s a lesson that must be remembered at Tory HQ right now. Having enjoyed large poll leads so far, and with an encouraging MRP from YouGov last night, this is precisely the time when the siren temptation to expand the target list comes a-calling.

It must be resisted. If anything, the campaign should be kicking the tyres and ensuring that its defence operation in Tory-held marginals is running properly, and ensuring its must-win target seats have all the resources that they need. A campaign is a complex thing, and myriad moving parts can easily go wrong.

The last election shows the importance of retaining focus, the polls already show some tightening of the Conservatives’ lead, and (as I discussed with John Curtice in this podcast yesterday) all the signs are that the severely underperforming Lib Dems are vulnerable to being squeezed by Labour. In short, things may well get tougher, and closer, before this election has run its course – as Dominic Cummings warned last night.

So if CCHQ’s eyes start once more to get bigger than their belly, they must be alive to the danger of over-reaching, and restrain themselves. If they stay disciplined, they might even benefit from Labour failing to do so – Buzzfeed reports that there are growing frustrations in the Opposition’s campaign machine that troops are being misallocated, either due to over-ambitious plans or discrimination in favour of hyper-loyal Corbynite candidates.