He has to do Brexit well, just as he thinks he can
He's going to continue to threaten to not pay the 39 billion and leaving with no deal . Which is going to send macron nuts. He desperately needs us to pay it. He's got enough problems in France without having to stump up billions of the French people's taxes and pay it to thr eu instead of us, it could even take down his Presidency. France will literally go into revolt and also likely demand to leave. It would be disastrous for macron.
It's a huge bargaining chip and Boris knows it. Macron is the one who has being making this hard for us, as he doesn't want France to also leave. Germany and France will really struggle if they need to cover our financial contribution. It's huge.
Boris is going to use this if he gets in as his way of getting further concessions. He will threaten We will leave with no deal and not pay.
And that can go one of two ways. Either he will get thr concesssions and we will leave with a deal. or he won't, and it's going to lead to a deep and hugely unpleasant divide with the eu, which will hugely damage both sides for years to come.
Either way If Boris gets in, we aren't going to see Teresa mays conciliatory approach. We are going to see something much tougher and much scarier.