By Lord Ashcroft KCMG PC.

The voters of Uxbridge & South Ruislip welcome the prospect of Boris Johnson as their next MP, according to my latest poll. My survey of 1,000 residents of the constituency, completed on Thursday, found that when asked which party they would vote for in a general election tomorrow, 42 per cent named the Conservatives, 28 per cent Labour and 19 per cent UKIP: a 14-point Tory lead.

But when asked how they would vote if Boris Johnson were their Conservative candidate, the margin extended to 29 points: the Tory share grew by ten points to 52 per cent, with Labour down five to 23 per cent and UKIP down three to 16 per cent.

Polling purists will tell you that you should not name one candidate in a survey without naming them all, as it places too much emphasis on one individual. Under normal circumstances that is quite true, but Boris is hardly a normal circumstance (though I suppose it is theoretically possible that one of the other parties is preparing to unveil their own blockbuster candidate in the Middlesex suburbs).

Even so, the results show Boris’s unique ability both to galvanise Tories and appeal to supporters of other parties. Under the standard voting intention question, 72 per cent of those who voted Conservative in 2010 said they would do so again; with Boris named as the candidate this rose to 79 per cent, with the proportion backing UKIP falling from 18 per cent to 13 per cent. The proportion of 2010 Labour voters switching to the Tories nearly trebled from 6 per cent to 16 per cent, and the numbers switching from the Lib Dems almost doubled from 18 per cent to 35 per cent.

The basis of his appeal, as I found in my research on the Boris phenomenon last year, is that for most voters in the constituency (53 per cent), including a substantial proportion of those who would usually vote for other parties, Boris is “different to most politicians, and in a good way”. Only 7 per cent said he was different “but in a bad way”; only one in three said he was “basically the same as most other politicians” and for one in ten he is “not really a politician at all”.

So it seems Boris would be a welcome and popular MP for Uxbridge & South Ruislip should he decide to stand there next May. But the voters were precisely divided over whether he should do so while doing his current job. Fifty per cent said they “would be happy for Boris Johnson to be both the MP for Uxbridge & South Ruislip and the Mayor of London until his term as Mayor comes to an end”. The other fifty per cent said he “should either wait until his term as Mayor ends before standing for parliament or resign as Mayor if he becomes an MP”.

Not surprisingly, most of the opposition to his serving as Mayor and MP simultaneously came from those who would not vote for him anyway. Even so, one third who said they would vote for Boris also said he should not do both jobs at the same time.

Most people in the constituency (71 per cent), including majorities of all parties’ voters, said that as Mayor Boris had “shown he is capable of taking on real responsibility”. Six in ten, including nearly seven in ten Tories, said they thought Boris “clearly has ambitions to become leader of the Conservative Party and Prime Minister”. Four in ten, still including a thin majority of Tories, said he “would be capable of running the country as Prime Minister”. Just over one third (35 per cent), still including a majority of Tories (just), said they thought that if he became PM “Boris Johnson would change Britain for the better”.

But when asked who would make the best Prime Minister, his potential constituents put David Cameron ahead of him, by 36 per cent to 33 per cent, with Ed Miliband on 19 per cent and 10 per cent naming Nick Clegg. Boris was the favourite among those who said they would vote UKIP in the standard voting intention question (by 43 per cent to 33 per cent over Cameron). Among those who said they would vote Conservative without Boris being named, 62 per cent preferred Cameron and one third named the Mayor.

Whether it is possible to be Prime Minister and still be regarded as “different to most politicians, and in a good way” is, of course, another question.

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