Regardless of expectations, losing local councilors in opposition is a bad sign. No party that has done it has gone on to win power. They are, for a number of reasons, more favourable territory for the opposition parties than general elections and opposition parties tend to underperform their local election performances at national elections.

There are however, two recent and important counter-examples: Jeremy Corbyn’s Labour in 2017 and 2019. There are, to my eyes, two persuasive explanations for that, but they have slightly different implications for the “what would be a good night for Labour?” question so I will take them in turn.

The first, which I’m leading with for the basic reason that it’s the one that I am currently the most persuaded by, is that Corbyn genuinely managed to change his party’s position between the local elections of 2017 and 2019 and the elections in the same year. I think that in 2017, a combination of a dire Conservative campaign and a effective Labour one meant that Jeremy Corbyn had won voters around between May 2017 and June 2017. In 2019, when the Labour party lost councilors and MEPs in May on a pro-Brexit position, a combination of the Conservatives’ change of leadership and Labour’s switch to a pro-referendum position helped them to corral some, but not all, of the voters they lost to the Liberal Democrats and Greens back to the fold.

If that is the case, then, essentially, what constitutes a good night for Labour hasn’t changed: but the good thing about a bad night is that we can say that if Labour takes the right steps afterwards they can overcome any problems. A good night in this scenario would be very simple: one in which Labour gained councilors and particularly in places where it does not currently have an MP.

What about the other explanation? The other one which looks to me to be plausible as well, is that Labour’s new core vote (like most parties of the European left their coalition is becoming younger, more graduate-heavy, more ethnically diverse and more concentrated in cities) is less likely to vote in second-order elections, when national power is not up for grabs, and that artificially depresses Labour’s performance in local elections.

The bad news here is that of course, the same features of Labour’s coalition that make local elections less useful as a predictor of general election outcomes make Labour’s electoral coalition particularly poorly-designed as far as winning power under our antiquated electoral system is concerned. If you are underperforming in local elections because at a general election, a bunch of graduates, ethnic minorities of all incomes and backgrounds, and the young are going to head to the polling station, then that means you will do better in places like Putney and Reading come election time. But Labour already holds Putney and one of the Reading seats and it is not certain that there are enough constituencies like Basingstoke, Worthing and East Shoreham and Bracknell, where the party’s new voters are all moving in greater numbers, to compensate for being unable to win seats like Morley and Outwood anymore.

On that read, a good night would be one in which Labour probably didn’t make very many overall gains because part of its vote just gives these contests a miss, but it became more competitive in areas with greater numbers of voters over 40, social conservatives and people without degrees, i.e. most towns and in the police and crime commissioner elections in Wales. They would give one of Andy Street and Ben Houchen a fright in their metro-mayoral contests. That, coupled with their core vote actually turning up at a general election, might suggest they were on course to win national power.

But there’s another complication this time: Labour is coming off the back of a landslide defeat. Yes, a landslide defeat that produced only a comparatively small Conservative majority compared to the Tory ones of 1983 and 1987 or the Labour ones of 1945, 1997 and 2001, but that is because it is getting harder for all parties to win majorities under first past the post.

The local elections of 1984 and 1998 saw the governing party finish ahead of the opposition as far as the projected national share of the vote - the estimate of how the parties would have fared had everyone in the country voted rather than just the parts with local elections – before the opposition reverting to type in 1985 and 1999. So should Labour be that worried if they do badly on the back of a landslide defeat this May? Perhaps not, because it may be that it is simply par for the course after a heavy defeat.

But perhaps they should, because not only did Labour lose in 1987 and the Conservatives lose in 2001, in both instances they failed to make meaningful advances, leaving them both essentially in the same place they were after their landslide defeats in 1983 and 1997. One limitation on analyzing elections is there aren’t very many, and the number of landslide election results is smaller still.

One thing I think we can say is: if I were Labour, and I had to choose, I’d much prefer to lose council seats everywhere than specifically in the seats they lost in December. The former suggests that they are feeling the usual after-effects of landslide defeat at a local election, and it is easier to see a recovery from. The latter would suggest a specific and new trend away from them in a specific type of seats: and that trend may be considerably harder to reverse than the familiar pattern was.