Boris Johnson’s chances of becoming Prime Minister are higher if Britain remains in the EU than if it exits
The argument goes like this.
If Britain remains in the EU that will be a victory for Cameron in the country as a whole, but the political benefit the current PM gets from it will be limited and short lived. With opinion polls prior to the referendum close, and neither campaign having yet inspired the country, the chances of a stonking large victory for Remain to boost Cameron look slim.
Remember Tory Party members favour Brexit 59% to 38% (see YouGov under first graph here) and will be annoyed the result is against what they perceive to be in their interests. This will strengthen the resolve of those among the parliamentary party to oust Cameron as soon as possible. As Matthew D’Ancona has written, MPs are split down the middle, and it takes only 15% of them (50 MPs currently) to call for a no confidence vote in the current leader. With Cameron already having promised to not seek a third term as PM, any such confidence vote would weaken him, potentially fatally even if the vote were not lost. With Osborne being both pro-EU and struggling after his recent budget, he is not going to be in a position to be able to beat Boris in the short term — polling of how the potential candidates shape up against each other can be found here. The way the Tories choose their leader is explained here — essentially the final two candidates go forward to a poll of party members, and those members favour Brexit, helping Boris.
So if Britain remains in the EU, Boris will be Prime Minister sooner rather than later.
If Britain leaves the EU it is actually much more complicated. The pound hit a 7 year low on the day Boris announced he was for Brexit, and that could be a taste for what happens after a Leave vote — no-one quite knows what would happen on the day after a Leave vote (and the government has been criticised for a lack of contingency planning), but I think it is safe to say that potential political and economic turmoil is going to take quite some handling, and indeed some time to handle short term until things calm down.
Britain voting to Leave would mean Cameron is politically toast, but not even the Tories are going to go for a leadership election if the pound is tanking and multinational businesses are stating they’re choosing to invest somewhere else. In this situation the fire would also turn on Boris for having helped take the UK over the precipice. A leadership election, pushed into the medium term, would be harder for Boris to win in these circumstances. It might not be Osborne who would profit, but there would be an anyone-but-Boris effort.
That might also be the reason by Boris is being, even by Boris standards, pretty damned awful at making the case for Brexit. Because saying he is in favour of it helps him, but it actually happening doesn’t.
Creative Commons Licensed Image from Flickr. Boris Johnson in Croydon by BackBoris2012 Campaign Team, November 22, 2011