This could have been the moment when Boris lost the next CON leadership contest

Being able to confront Ed was an opportunity that he fluffed

For me one of the best bits of TV during the campaign was at the end of yesterday’s Andrew Marr show when the programme’s two main participants traditionally join each other on the sofa for the closing couple of minutes. This time it was Boris and Ed and the wide judgement was that the Mayor lost.

This is how Nick Robinson saw it.

Wonder how many Tories still think Boris is their under-used secret weapon after this morning's performance on the Marr sofa? — Nick Robinson (@bbcnickrobinson) April 26, 2015

The timing is important because we could be only a couple of weeks away from a Conservative leadership contest even if the Tories do win most seats. It is hard to see Cameron staying if he ceases to be PM and there are those saying, unfairly in my view, that he should stand aside anyway if his party fails again to win an overall majority.

A Conservative contest involves two very distinct phases. Firstly the Parliamentary Party has a series of elections to decide which two candidates should be put to the party membership in a postal ballot.

The history of these contests is such that odds on favourites, like Michael Portillo in 2001, don’t even make it to the final cut. Then it will be recalled that Portillo failed by two votes to make the top two in the MPs ballot which left IDS and Ken Clarke being the ones left to fight it out in the membership vote.

Boris Johnson has not been an MP since 2008 which means that in the likely post general election parliamentary party many won’t really know him – a fact that might hamper efforts in the first phase. There has always been a risk that he could suffer a fate similar to Portillo.

If it does come to a contest you can bet that the mayor’s detractors will be using the above clip to undermine him. Methinks Boris would struggle to win a 2015 contest.

Mike Smithson

For 11 years viewing politics from OUTSIDE the Westminster bubble

For latest polling and political betting news follow @MSmithsonPB

