The Conservatives themselves have been hit by 2 defections by sitting MPs to UKIP: Douglas Carswell and Mark Reckless. Both of them have resigned their seats to contest by-elections, which appears to be a strategy to keep the political pressure and momentum running in UKIP's favour: with staggered out by-elections in the lead up to the general election, UKIP could have the Tories constantly looking over their shoulders for UKIP.
But if the decision to stay or leave the European Union is a pragmatic decision for Cameron (if, I suspect, one where the security of his premiership weighs quite heavily as a factor), it's a reckoning for others. John Redwood, a former Conservative cabinet minister, has warned businesses not to speak out in favour of remaining within the EU:
"If they don't understand that now they will find those of us organising the 'get out' campaign will then make life difficult for them by making sure that their customers, their employees and their shareholders who disagree with them - and there will be a lot who disagree with them - will be expressing their views very forcefully and will be destabilising their corporate governance."
It's not often you hear a Tory talk about destablising corporate governance! (I can't wait to see Redwood camped outside the Confederation of British Industry telling worker of the world to unite). For me this sums up how much leaving the EU has become an article of faith for much of the Conservative party. Leaving the EU itself seems to be a symbol for being able to push ahead with other right-wing policies: cutting red tape, getting even tougher on immigration, cutting taxes... When Cameron was first elected leader of the Conservative party, he wanted to detoxify the Nasty Party, but now much of the party is set on turning to "true conservativism" in the belief that this is the only way for the party to win (or be worthy of winning) elections. And increasingly the Conservatives are equating true conservatism with UKIP.