As far as the poll numbers go if I recall rightly May had a bigger lead when she called an election and proceeded to lose 30 seats? The reality for Johnson is that even if he engineers a No Deal Brexit the election can't happen until after people have had a chance to experience the consequences and a poll lead could evaporate pretty quickly in those circumstances.
It is possible we will see the so called "Churchill" effect, if the UK leaves on the 31st October, in any following election.
The Brexit party will be redundant, and the Liberals have prematurely cornered themselves as a remain party. The electorate being sick of Brexit will not want to return to the subject but rather focus on the issues facing the country.
The focus on Brexit voters has often included immigration as being the main reason, but I remember hearing and reading that many in the North of England and Wales voted to leave as a big middle finger protest vote to a perceived London centric UK.
I do not think that the political antics over the last few years in London will have impressed these voters much.
In addition, Boris has recently promised all this money for extra police, NHS etc, out of nowhere, and it will be easy for others to propose a manifesto pledging extra spending based on these figures. Again, premature promises from BoJo who probably thought an early election was in the bag.
In the future hustings, debates and political broadcasts, the Tories would not be able to diss completely any proposed increased spending plans based on these figures by other parties leading up to election, since they will be admitting to the lies of their leader.
If anti London centric feelings remain strong and the Brexit Party and Liberals fall out of contention, Labour, even with Corbyn, might do surprisingly well. If Labour fights on poverty, social divides, North South differences then they could do much better than expected.
