Thread by @centrist_phone

We need to talk about the Brexit Party.

Their withdrawal from Tory held seats increased the national Con vote share from an average of 39% to 42%.

But this increase, in terms of gaining Lab seats, is worth nothing. And is likely to benefit Lab.

Why? Let's find out...

1/8

The withdrawal of the Brexit Party from Con seats achieved two things for Con;

1) It made retaining existing seats a bit easier

2) It increased their vote share in those seats, and thus increased their national vote share

It did not increase their vote in Lab seats.

2/8

In Lab seats where Brexit party is standing, two things are true;

1) Brex are attracting Lab Leavers who voted UKIP in 2015 and Con in 2017

2) They are attracting more Con voters than Lab voters, due to there being far more Con leavers

Let's look at the impact of this.

3/8

To give an example.

A typical 65% Leave voting Lab marginal. 40% Lab voters and 40% Con.

Lab voters = 60/40 remain
Con voters = 20/80 leave

Brex come along. They take 25% of leavers from both parties.

That hurts Con more:

Lab: 36% (-4%)
Con: 32% (-8%)

4/8

In the above example:

1) The same percentage of leave voters are switching from Lab to Brex and Con to Brex

2) This hurts Con more because they have a much higher base of Leavers

Even if Brex took more Leavers from Lab, say 60/40, it would still hurt Con more.

5/8

So, it's very unlikely that the Brexit party standing in Labour seats helps the Conservatives.

Then there is the national vote share

Con national % in polls is inflated by around 3% due to the Brexit party not standing in Con seats.

This 3% increase in VI won't win seats

6/8

When trying to calculate seat gains, people use swing from one party to the other.

But 3% of that Con lead, in terms of the marginal battlegrounds, is an illusion. It counts for nothing.

Yes, it helps them defend seats. But it won't take a single marginal for them.

7/8

The net impact of the Brexit party standing in Lab only seats is this:

1) An illusionary 3% boost to Con vote share that achieves no gains

2) It is now harder for Con to win Lab Leave seats

It's surprising how few political commentators have understood these simple facts.

END