UK 2017 General Election

Tactical Voting - What If?

What if 0% of voters who voted for a progressive candidate that finished below another progressive candidate, had instead voted for the best-placed progressive candidate? (Progressive parties are taken to be Labour, Lib Dem, SNP, Green, or Plaid Cymru.)

Move the slider to the right to increase the propensity of voters to vote tactically.


In the UK, elections are held using a 'first past the post' system. The UK is divided into 650 contituencies, from each of which the candidate who receives a plurality of votes is returned as a Member of Parliament (MP).

It is a peculiarity of the UK system that although MPs are returned by a plurality of votes, the UK resists reducing to a two-party system. Multiple parties stand candidates in each constituency.

Labour are the major left-wing party. They compete for voters who support a progressive agenda with Liberal Democrats, Greens, the Scottish Nationalist Party (SNP), and Plaid Cymru (PC). This is complicated because SNP and PC are also nationalist parties, who seek independence for Scotland and Wales from the union respectively. In England, Labour also compete for voters with the UK Independence Party (UKIP), who are a nationalist party who seek independence of the Union from Europe.

The Conservatives are the major right-wing party. They have little competition for the conservative agenda, though they compete for voters from the UKIP.

This political landscape requires many broadly progressive voters to choose between supporting the candidate that best fits their political views, and supporting a candidate most likely to frustrate the Conservatives. In a constituency in which Liberal Democrats have historically run third behind Labour and Conservatives, a natural Liberal Democrat may decide to vote for the Liberal Democrats, or tactically against the Conservatives, by voting for the best placed progressive party, Labour. Likewise for a Labour supporter where Labour runs third.

Of course, it is extremly reductive and over-simplistic to imagine that - for example - every Liberal Democrat would break for Labour in a fully tactical-voting scenario. Some may vote tactically for the Conservatives to frustrate Labour! These limitations are acknowledged but ignored for the purposes of simplicity. The results should be treated with an appropriate degree of skepticism.

Alec McEachran, June 17 2017