If the Brexit Party wants their ideal Brexit, they need to go big or go home

The UK will leave the EU on 12 April 2019. Or not.

The plan was that today would be the United Kingdom’s first full day outside of the European Union. And judging by the protests in Westminster yesterday, many people who voted Leave are not happy about that. Many have referred to the happenings in Parliament as the “death of democracy”, seemingly forgetting who put MPs into Parliament in the first place.

Of course, with speculation of a general election possibly imminent, a certain Nigel Farage might attempt to take advantage of this populist mood. His newly-formed Brexit Party (note: different from UKIP) is somewhere between 1% and 5% in the polls, which isn’t overly impressive. But I wanted to explore how much of this mood that Mr. Farage would need to tap into if he wanted to add extra Parliamentary pressure to get his version of Brexit.

It will come as very little surprise that the majority of Leave voters voted for the Conservatives at the last election. According to Survation, who conducted the most accurate final poll of the election campaign, nearly 63% of Leave voters voted Conservative, 24% voted Labour, 4% voted UKIP, 3½% voted Lib Dem, and nearly 6% for everyone else. (Most other polls gave broadly similar figures.)

With that said, and using the estimates for the Brexit Result by Constituency and the General Election results from the House of Commons Library, we can come up with an estimate on what share of the vote the Brexit Party might need in order to reach various levels of influence in Westminster.

(Note: Polls are generally showing virtually no swing between the Conservatives and Labour at the moment.)

Of course, we can’t apply a uniform swing on the Brexit Party, as it’s probably safe to assume that next to no Remain voters would even consider voting for them. So instead, we will increase the share of the vote for the Brexit Party proportionally to the estimated Leave vote in each constituency.

First Past the Post makes it quite difficult for a party to get into Parliament, but the Brexit Party could cause grief for the Conservatives without any MPs. If they get 20% of Leave voters (10% of all voters) to vote for them, assuming they are proportional to how Leave voters voted in 2017, that would be enough for Labour to become the largest party in the House of Commons. At this level, it would more than likely make any Brexit more difficult to achieve.

In order to get their first seat Parliament, the Brexit Party would need to get around 45% of Leave voters (23% total) to support them.

The first seat that they would likely get is Thurrock (Essex), which voted just over 70% to Leave. In the general election, the Conservatives won Thurrock by less than 1% over Labour. UKIP, though, got 20% of the vote in Thurrock, the highest in the country.

Of course, at this stage, Labour would still be the largest party, with either the SNP or Lib Dems providing them with a majority. So even though the Brexit Party would officially have a say in Parliament, Brexit would still be unlikely at this stage.

By the time the Brexit Party gets to 56% of Leave voters (29% total), they will have surpassed the Lib Dems and SNP in Parliament, to become the third largest party on 55 seats. A sizable voting block indeed by this point, but still not enough to block Labour and the SNP teaming up to prevent their preferred Brexit from occurring.

To put this figure into context, in 2010 the Liberal Democrats reached a similar number of seats, but with a smaller share of the vote (22%).

After this point, we start to see their seat count skyrocket. Once they get to 62% of Leave voters (32% total), they will surpass the Conservatives to become the second largest party in the House of Commons, with 144 seats. Whereas before this point they were taking mostly Conservative-leaning Leave constituencies, now they start to take some Labour-leaning Leave constituencies as well.

Once they get to 68% of Leave voters (35% total), they will surpass Labour to become the largest party, with 240 seats. Meanwhile, the Conservatives, on 84 seats, would be on their worst result since its predecessor party (the Tories) was founded in 1678.

Between them, the Conservatives and Brexit Party would have a de facto majority in the House of Commons. However, the only Conservatives that would remain in Parliament would be coming from Remain constituencies, which would mean that the rump party may not be as willing to support a Brexit Party government, so it’s unclear whether they would be able to form a government.

If 75% of Leave voters (39% total) decide to support the Brexit Party, it is at that point when they would get an overall majority in the House of Commons. (This figure is comparable to what the Conservative Party would need today.)

How the popular vote of the Brexit Party would impact potential seats in the House of Commons. (BREX dark blue, CON light blue, LAB red)

According to an Opinium poll conducted last week, around 74% of Leave voters prefer to leave the EU without a deal, as opposed to a delay or revocation of Article 50. In order for the Brexit party to form a government to actually form a government, they would need to convince all of them to vote for them in an upcoming election, which is not realistic.

Instead, the Brexit Party may find itself in an interesting First-Past-The-Post Paradox, in that the more votes that they get, the less likely it is at the Parliamentary maths will allow them to get the kind of Brexit that they want. So unless they’re able to mobilise virtually all No-Deal supporters to come on board, their very existence will actually do their cause more harm than good.

I am Joe. I am a techy at heart, a self-taught psephologist (political number cruncher), a pleasure cyclist, and someone who just calls things as he sees them.

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