22 October 2018updated 08 Jul 2021 11:08am

Who benefits if two million people register to vote this week?

Ballot papers are counted during the Brecon and Radnorshire by-election count at the Royal Welsh Showground in Builth Wells, Wales on August 2, 2019. - Britain's Boris Johnson faces his first test at the ballot box Thursday in a by-election that could reduce his parliamentary majority to just one, as his new government vowed to double funding for a possible no-deal Brexit. Johnson's Brexit plan could also become harder to enact as his governing Conservative Party looks set to lose the Welsh seat of Brecon and Radnorshire to a pro-Europe candidate on Thursday. (Photo by Isabel INFANTES / AFP) (Photo credit should read ISABEL INFANTES/AFP via Getty Images)

Since the election was called, millions of people have registered to vote. What does it mean, and who benefits?

Well, the short answer is: “it’s complicated”. Thanks to two separate changes: legislation brought forward by the Conservative government on how electoral registration works, and the changing nature of our housing market, voters are a lot more mobile than in the past, thanks to instability of the private rented sector. Most MPs in urban constituencies lose about a third of their data this way every year.

So a lot of people registering to vote are doing the political equivalent of patting your pockets down to make sure you have your keys on you: they have likely already registered, but are registering again just to make sure. In addition, most are in seats where, thanks to our iniquitous electoral system, their votes won’t matter.

However, some will be actually registering, and statistically speaking, the majority of people who fall off the register will be people at the start of their lives who are geographically mobile, and are therefore more likely to vote Labour, Liberal Democrat or Green. And them falling off the register has big implications for how our political parties operate, too.

Persuading voters to vote tactically (in other words, to think long and hard about how they feel about the parties before picking the Conservatives or whichever party is best-placed to beat them locally) is a big part of how all the parties operate, particularly and most significantly the Liberal Democrats. Doing that is a two-stage process: first, find the voters who might vote tactically for you, and, second, persuade them. Most people in most of the country know that they have a straight choice between the Tories and Labour, and one reason why Labour did unexpectedly well in the last election in areas of traditional Labour weakness was that anti-Tory voters moved from Conservative-Labour seats to Conservative-Liberal Democrat seats, and took their voting behaviour with them.

In the long term, that makes Labour competitive in many places they once would not have been. In the short term, it makes it harder for the Liberal Democrats to attract tactical voters.

Thanks to those changes in British society and electoral regulation, registering to vote doesn’t tell us anything necessarily – but its absence would be a bad sign for every party other than the Conservatives.