The Conservative Party now has 81 leaders

By Tim Montgomerie
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Why has David Cameron taken the position on an EU referendum that he has? Tory members credit one factor above all others - the 81 Conservative MPs who rebelled last year.

We asked the following question:

"On a scale of -5 to +5 where -5 is very counterproductive and +5 is very powerful, please say which of the following factors have been most important in encouraging David Cameron to move towards holding an EU referendum?"

These were the results:

• The rebellion last year of 81 Tory MPs, calling for a referendum: 2.96
• The nature of events in Europe, especially the possible movement of other nations to fiscal union: 2.90
• Opinion polls showing the British people want a vote on Europe: 2.85
• The growing threat of UKIP: 2.69
• The private encouragement of Eurosceptic ministers like Iain Duncan Smith and Owen Paterson: 2.32
• Eurosceptic newspapers: 2.21
• The Prime Minister's own personal convictions: -0.27

It is interesting that UKIP gets a big acknowledgement too. Ukippers would undoubtedly argue that their party's current strength in opinion polls also helps explain the rebellion of the 81.

This is the second of three blog posts on the results of yesterday's EU survey. The first found backing for Cameron's position on the timing of a referendum and for Dr Fox's position on the timing of renegotiations.