The possibility of a Conservative victory in 2015 is one of the Yes campaign's biggest trump cards.
Former Tory attorney general says proposal to prevent British terror suspects from returning home would "offend basic principles of our own common law".
The decision of nine Conservative MPs elected in 2010 to stand down suggests many fear defeat - and makes it more likely.
Douglas Carswell set for landslide victory after his defection to Ukip from the Tories.
Had the PM refused to promise a referendum, he would likely have been deposed as Conservative leader.
Leading Tory eurosceptic says Carswell's decision doesn't make sense after Cameron's EU referendum pledge.
The party's best hope of defeating the defector lies in winning tactical support from centrist voters.
The PM is not alone in failing to articulate a clear set of principles for this new era.
Farage needs to explain why he could prevent the referendum he has always wanted.
Rather than choosing a former Ukip leader as their candidate in South Thanet, the party should have selected a liberal figure capable of winning tactical votes.