A new British centrist party would likely benefit the Tories, just like the last time

An unpopular Conservative government, a left-wing Labour leader with poor favourability ratings, and a breakaway faction of centrist Labour MPs joined by a Conservative defection a short while afterwards. The parallels between the formation of the Independent Group of MPs in February 2019, and that of the Social Democratic Party in 1981, are clearly apparent. Could a new centrist force make a breakthrough in a Westminster general election, as the alliance between the Liberals and the SDP famously failed to do at the General Election in 1983?

Eyebrows were raised at a poll by YouGov on the 20^th of February, which suggested that 14% of voters would back The Independent Group if they were to stand as a separate party at a General Election, with a further 7% saying they would vote for the Liberal Democrats. Their combined total of 21% is not far behind the 25.4% of the popular vote that the Liberal/SDP alliance received in the 1983 election. The YouGov poll also had Labour on 26%, which is also close to the 27.6% vote share that Labour won in 1983.

To gauge how successful a new third party alliance between the Lib Dems and the Independent Group might be at a Westminster election, I took the 2017 General Election results and re-allocated votes according the cross-tabs on the 20^th of February YouGov poll. For example, 12% of those who voted Conservative in 2017 said they would either Lib Dem or Independent Group at the next election, 24% of 2017 Labour voters said the same.

I have assumed that the Independent Group, or any successor party, will come to some sort of alliance with the Lib Dems in the same way that the Liberals and the SDP did in the 1980s, because it would be plainly absurd if the two entities were to attempt to compete for the same voters in a first-past-the-post election.

A comparison between the 1983 election and a hypothetical election with the results suggested in the YouGov poll can be found in the table below.

As you might expect, a third party polling in the low-20s, with Labour polling in the mid-20s would result in a similar electoral outcome to the 1983 election, with the Conservatives receiving a substantial benefit from a split opposition vote (except with the SNP holding dozens of historically Labour voting seats). The chart at the top of the page on the left shows how seats moved between the elections in 1979 and 1983, whilst the one on the right shows how seats might move if an election was held tomorrow and the parties received the number of votes suggested in the YouGov poll.

Despite a much improved result in terms of the popular vote, a new third party would only be expected to make a handful of gains, such as the formerly Lib Dem Labour seats of Bermondsey and Old Southwark, Cambridge, Leeds North West and Sheffield, Hallam; the currently Conservative seats of St Ives and Richmond Park, and North East Fife, where the SNP currently have a majority of two.

A key problem that a prospective third party challenge on Westminster faces is that, due to the collapse in the Lib Dem vote since the 2010 General Election, there are few constituencies where the Lib Dems are currently even close to being the largest party. Other than the 12 seats that they won in 2017, there are only 9 seats where they were within 10 percentage points of the winner, and only a further 10 where they were within 20 points of the winner.

The dearth of third party pickup opportunities means that, even if a potential third party/Liberal alliance were to poll a quarter of the popular vote, it would likely amass uselessly in seats where a third party can’t win. Even if a new third party were to do better than their 1983 forbears and beat Labour in the popular vote, it would be difficult for them to gain many more than 30 seats.

However, a strong showing from a third party would move a substantial amount of seats from the Labour to the Conservative column, in exactly the same way as in 1983. I’ve put a forecast for each seat in a Google spreadsheet here.

Another striking similarity with the early 1980s is the unpopularity of the Labour leader. Jeremy Corbyn’s net favourability (the percentage of people who say they approve of the job he is doing as leader of the Labour party less the people who say they disapprove) was -55% in the February 2019 Ipsos MORI poll. This is the worst favourability rating of any opposition party leader since the nadir of Michael Foot’s unpopularity in 1982.

The chart below compares Jeremy Corbyn’s net favourability score over his tenure as party leader with other leaders over the first 42 months in the role (the dashed line indicates they were Prime Minister at the time). Again, the comparison with the Labour party of the early 1980s is apparent.

Despite the unpopularity of the Conservative government and the Labour opposition, the maths of operating in a first past the post environment makes it extremely difficult for a third party to make a serious challenge in Westminster elections in England.

However, if the current Tory government end up presiding over a disaster in the wake of a chaotic departure from the European Union, then who knows what manner of black swan events may happen in British politics. We may be awaiting a 1980s revival for a little longer yet.

Peter Donaghy (Salmon of Data)

A qualified accountant and data analyst, interested in politics, economics and data. Twitter: @peterdonaghy

www.salmonofdata.com