With the exception of 2017, no government has ever done worse in a general election than the preceding local election. In fact, the overall trend is for the governing party to not only do better, but a lot better in a general election than they do in local elections, because voters tend to use them partly to send a message to the incumbent at Westminster.
So the question of what would be considered “a good night” for the Conservatives in the local elections in May is a lot less complex than it is for Labour or the Liberal Democrats, as the brief is simple: don’t get hammered. The party should, all other things being equal, feel confident in its ability to hold onto any constituencies where it places, let alone where it actually holds or – much, much, much less likely – gains seats.
There is a limit to that, however. While, all things being equal, say, Justine Greening might be able to hold Putney if the Conservatives were to lose every councilor in the six Wandsworth wards that make up her seat, losing local government representatives erodes your party’s activist capacity. (While it might not be wholly desirable that defeated councillors tend to be less willing to campaign every weekend than incumbent ones, it is nonetheless true.) It also reduces the local influence and reach of the MP which makes it harder if they are hoping to run slightly against the national platform of the party – and I think it is likely that Greening and others in seats like hers, like Mark Field in Cities and Westminster, will want to.
So on a good night the Tories would suffer heavy losses but retain enough of a presence in the seats they hold not to further add to their crisis of a small and shrinking activist base. A bad night would be one where constituencies where the Tory MP is in opposition to the local council – like Amber Rudd in Hastings, which is Labour-run – the Tory opposition is shrunk or goes extinct. (In Hastings, the Conservatives hold just eight seats, of which five are being contested this time.)
In addition, it would be a good sign for the Conservatives if Labour’s “suburban discomfort” continued. Even as Labour has gained votes since leaving office in 2010, it has lost ground in seats like Ed Balls’ old Morley and Outwood, a once-safe Labour seat that now has a significant commuter population, lost in 2015 and still Tory in 2017, or Natasha Engel’s North East Derbyshire, which went Conservative for the first time since 1931 in 2017. In addition, the party did worse in constituencies with significant Jewish populations. In fact, had Labour performed as well in those areas than it did in other urban areas, it would now be in Downing Street, albeit with an incredibly fragile parliamentary position. So holding onto Hillingdon, Barnet and Tamworth would be a positive sign for the party.
So anything which indicates that Labour continues to struggle in these type of seats would be a good sign for the Conservatives, as it would indicate that the Labour path to a working parliamentary majority is not clear, to put it mildly. However, it was be a very bad night if the Conservatives were to lose Wandsworth and Westminster, despite the excellent spin operation they have mounted about their prospects in those boroughs. Ultimately if a situation in which the Conservatives can only win 20 out of the 56 seats that are up for grabs continues it is, as with Labour’s suburban problem, tricky to see how they will win not just working parliamentary majorities but ones which allow them to enact anything radical for the foreseeable future.