This June’s British election saw a surprise as Theresa May’s Conservatives, who were expected to increase their majority at the beginning of the campaign, lost their majority and almost lost government altogether. The election was seen as a success for Corbyn’s Labour party and an utter failure for May’s Conservatives. What is notable, however, is that the vote for both the Conservatives and the Labour party went up compared to 2015. May’ proportion of the vote was 5.5 percentage points higher than Cameron’s in 2015 while Corbyn’s was an impressive 9.6 points higher than Milliband’s. In contrast, both the UK Independence Party (UKIP) and the Scottish Nationalist Party (SNP) lost large numbers of votes. May did not lose the Conservative majority because she won fewer votes than Cameron, she lost because Labour was able to increase their vote share to a greater degree than the Conservatives were.
This suggests that Labour was able to take votes from the collapsing UKIP. UKIP had a disastrous election, losing its only seat and dropping over 10 percentage points in the popular vote. Part of the narrative around Labour’s rise and UKIP’s collapse is that Labour was able to win back working class, anti-immigrant voters who defected in 2015. A look at where UKIP lost votes and where Labour and the Conservatives made gains, however, suggests that the Conservatives benefited more from UKIP’s decline than Labour did. The more UKIP lost in a riding, the closer Conervative gains where to Labour ones.
The graph below shows compares the gains of both Labour (in red) and the Conservatives (in blue) to UKIP losses. Each x marks the change in percentage points for either Labour or the Conservatives in a particular riding, while the line provides the overall trend. Labour tended to pick up votes in a riding regardless of whether UKIP suffered significant losses. There is a slight increase in the Labour vote share as UKIP losses increase, but it is only slight. In contrast the steeper trend line for the Conservatives shows that the more UKIP lost in a riding the more successful the Conservatives were. Where UKIP lost 0-10 percentage points the Conservatives tended also to lose support (though there were a substantial of ridings where UKIP losses were close to 0 and the Conservatives made substantial gains). In contrast, almost all of the ridings in which UKIP lost more than 10 percentage points saw Conservative gains, many of them quite substantial.
This is not to say that Labour did not make gains in ridings in which UKIP suffered substantial losses. Like the Conservatives, Labour only suffered losses in a couple of ridings in which UKIP lost over 10 percentage points of the popular vote. There is, however, a much larger gap between the two parties in the ridings where UKIP losses are low. The more UKIP losses in a riding, the closer the Conservatives come to catching up to the Labour party’s gains. In the vast majority of ridings the Conservative gains never fully catch up to Labour’s gains (though the one riding in which UKIP saw losses of over 30 percentage points, Clacton, saw a much larger Conservative gain than a Labour one). The gap between Conservative and Labour gains is much smaller, though, in ridings where UKIP lost over 15 percentage points than in ridings where the UKIP vote dropped by fewer than 15 percentage points.
While this suggests that Labour might have taken votes from UKIP, the UKIP decline was more important to Conservative success than Labour success. The fact that Labour made large gains regardless of whether riding saw a substantial UKIP collapse suggests that Labour was able to take votes from other parties (or that they were able to mobilize large numbers of previous non-voters). Indeed, UKIP’s collapse may have done more to hurt Labour than to help it. Had UKIP not lost large numbers of votes, the Conservatives may not have been able to make the gains that they did in the ridings where UKIP vote declined by more than 10 percentage points. A larger gap between Labour and Conservative gains in these ridings may have handed a number of seats that Conservatives won over to Labour.
The same dynamics do not appear to apply to the SNP in Scotland. The graph below shows that the Conservatives made substantially larger gains than Labour regardless of how much the SNP lost in a riding. Labour did slightly better in ridings where the SNP did worse as compared to ridings where SNP losses where limited, but the increase in Conservative vote share appeared to be unaffected by SNP losses. The result is a reasonably consistent gap between Conservative and Labour gains throughout Scotland.
The Labour party’s success in the 2017 election was remarkable. It is particularly notable that Labour did not need to see large UKIP losses in a riding in order to make significant gains. This suggests that, while Labour probably did win over some former UKIP voters, they also had other sources of support. The Conservatives, meanwhile seemed to be much more reliant on making gains from UKIP losses, suggesting that the fortunes of UKIP have a much greater impact on the Conservatives than on Labour.