After every by-election I write pretty much the same blog post. By elections tell us almost nothing about the state of public opinion, but are nevertheless extremely important in setting the political weather. This one is no different.

First, why they don’t tell us much. By elections are not little mini general elections. They take place in but a single constituency, which is not necessarily representative of the country as a whole. Richmond Park is an extremely affluent slice of South West London – it is not like other places. In a by election that it appears the Lib Dems successfully steered onto the issue of Brexit it is wildly unrepresentative – on Chris Hanretty’s estimates it voted 72% to remain, making it one of the thirty most remainy constituencies in Britain (and the fourth most remainy out of the 330 Tory constituencies). Secondly, by elections don’t change the government. In a real election the public are heavily influenced by issues like who they trust to run the country, who will the best PM. By elections don’t change that, so there are different dynamics. Thirdly, the intensity of campaigning is different, so larger swings are common. Campaigning was a particularly unusual issue here because Goldsmith was running as an independent – while some conservative MPs came to help him out, he did not have the might of the Conservative party machine behind him, while the Lib Dems appear to have thrown the kitchen sink, worktop, cooker, etc at it.

So it’s an unusual event in an unusual area that, in isolation, tells us little. It does, however, serve as an illustration of a wider pattern we’ve been seeing in local government by elections, where the Lib Dems have been doing very well. Lib Dems always out perform in local by-elections (and simplistic analyses of them has long been a straw for their supporters to grasp in dark times) but even by their own high standards they’ve been pulling out very positive results that have not been reflected in national polling. My best guess is that the explanation for this is something along the lines of people having stopped wanting to punish the Lib Dems. Having seen them humiliated and almost wiped out of parliament, they think they’ve had their medicine and now when a nice Lib Dem candidate comes along in a by-election people are again willing to give them a hearing. They aren’t doing well at a national level because people don’t hear them – they are the fourth party in votes and seats and struggle to get much coverage.

The impact of this victory will, therefore, be important. It will get the Lib Dems a hearing, remind people they are there and can win. Expect to see a Lib Dem boost in the national opinion polls, like they enjoyed after by-election victories years ago. The Lib Dems have a long history of using by election victories to show they are a viable party and to get themselves noticed. This could be another.

There’s another important impact too, that on the crude Parliamentary maths. Theresa May had a majority of 12, now it’s 10. As that is whittled away defeats become more likely…and an early election becomes more likely. The by election tells us little about what would happen in such an early election. Richmond Park is an extremely pro-EU seat, while a general election would be fought in a country that voted for Brexit. More than three-quarters of Conservative seats voted to Leave (and most those those that didn’t were far closer than Richmond Park). Don’t imagine that the swathe of Lib Dems seats the Conservatives won in 2015 are all itching to go back to the Lib Dems purely on the issue of Brexit – looking at Hanretty’s estimates, 20 of the 27 Lib Dem seats that the Conservatives gained in 2015 voted to Leave the EU.

Previous polling has suggested that the Lib Dems could indeed do very well in an early election fought around the issue of Brexit, and I think that is the case (especially if they are the only explicitly pro-membership party and can win pro-European support from Labour). Nevertheless, those same polls also suggested a very solid overall win for the Conservative party. Britain is NOT just a bigger version of Richmond Park.