When looking at the results of the last general election, is it very easy to judge the effect of a party by the number of seats it won. Despite getting almost 4 million votes, UKIP only won a single seat, and so were often said to have had little effect on the outcome. However, it is easy to overlook the fact that in a First Past The Post system, UKIP votes may have come at expense of one of the larger parties, and so may have changed the results despite not winning the seat.

Take, for example, the seat of Barrow and Furness:

Here, we have a clear example of how UKIP did not win the seat, but may have prevented the Conservatives from winning.

Unsurprisingly, the opposite also exists, as happened in Bedford:

Here, Labour could potentially have won the seat if it weren’t for UKIP taking votes from them.

It is important to here challenge the idea that UKIP voters are a ‘far right’, and are naturally Conservative voters if UKIP aren’t an option. While that is certainly true for a large number of UKIP voters, the party’s demographics, especially in terms of economic background, more closely match that of Labour, and the UKIP manifesto made several notable attacks on Conservative policy in line with Labour, for example condemning the ‘Bedroom Tax’ and promising to repeal it. As such, UKIP is liable to take voters from both parties, and if it were to collapse, its voters would be split between the parties, not solely going to back to the Conservatives, although polling data does suggest that people who voted UKIP in 2015 were more likely to have voted Conservative than Labour in 2010.

While there is no perfect way to show how UKIP may have affected the results, below are the seats where the UKIP vote was more than twice the vote difference between the Conservatives and Labour. Readers should note this method, as applied to future voting predictions, is entirely arbitrary, but works well to show the potential UKIP have to change the outcome of the next election.

Firstly, the seats that Labour could lose – in total, 31 seats, as shown on the map below:

Note that although UKIP did not have a strong turnout in London, it could be enough to change 5 Labour seats there.

The Conservatives have slightly less to worry about, with only 23 at risk:

The 54 seats above represent one possibility of what could happen in 2020. The referendum in 2017, depending on its results, could mean the collapse of UKIP, but as Scotland has shown, it’s also entirely possible that their vote will go up again. The same is true for their huge vote resulting in only a single MP – voters could become disillusioned at the unfairness of their situation, but could also get fired up and push harder to get what they want. Either way, both Labour and the Conservatives will need to understand that UKIP’s influence exceeds its single MP. Labour need to win all the Conservative seats they can get to have a chance at power in 2020; the Conservatives, at only 6 MPs over the magic number of 325, will have to fight hard against UKIP’s gains if they are to retain their majority.