Choosing Boris Johnson over Jeremy Hunt is only worth 2-4 percentage points of extra vote share, but either candidate delivering Brexit would provide the party a 12-14 point boost
I have argued in a blog post at ConservativeHome that Boris Johnson’s ascension would not automatically equate to the return of Brexit Party defectors. I said that the key to winning back these Farage Tories likely lay in the actual delivery of Brexit rather than a promise to do so after another General Election.
Paul Goodman, good editor that he is, then challenged me to explore this theory further and so, with all the attendant caveats of the dangers of polling hypotheticals here it is.
In a nutshell, the data bears the theory out. If the Conservatives deliver Brexit under Jeremy Hunt or Boris Johnson, Farage Tories return. If the Conservatives fail to deliver Brexit and are forced into a general election instead, their Brexit Party defectors cleave to Farage.
In terms of how the frontrunners and the scenarios line up we can see that Johnson does perform slightly better than Hunt, but not by a significant extent. Who the leader is seems to make between 2 and 4 percentage points of difference. The key is whether Brexit has been delivered or not, that changes Conservative support levels by between 12 and 14 points.
In short, Johnson may be a little more appealing, but the impact of that is insignificant compared to whether or not Brexit is delivered.
The upshot is this: the next Conservative Prime Minister would be well advised to use this current House of Commons to deliver Brexit - deal or No Deal. The alternative of a ‘we’re almost there’ General Election even under Boris Johnson could well result in dramatic Brexit Party gains.