Sitting Tory MP for Clacton, Essex, Douglas Carswell stunned the Conservative Party yesterday. He announced in a live press conference that he was defecting to UKIP and would be standing for Nigel Farage's party in a subsequent by-election.
Mr Carswell said the decision to defect from the Conservatives had given him "sleepless nights" but he wanted to see "fundamental change in British politics" and UKIP - a party he believed belonged to members rather than a "little clique" of political insiders - could deliver it.
"This has not been an easy decision. I have been a member of the Conservative Party all my adult life. It's full of wonderful people who want the best for Britain."
"My local Conservative Association in Clacton is thriving. It brims with those I'm honoured to call my friends."
"The problem is that many of those at the top of the Conservative Party are simply not on our side. They aren't serious about the change that Britain so desperately needs."
"Of course they talk the talk before elections. They say what they feel they must say to get our support... but on so many issues - on modernising our politics, on the recall of MPs, on controlling our borders, on less government, on bank reform, on cutting public debt, on an EU referendum - they never actually make it happen."
He said only UKIP could "shake up that cosy little clique called Westminster."
Mr Carswell's damning verdict of the establishment didn't stop there either. He went on to criticise Mr Cameron's promise of an in/out referendum come 2017. He claimed the Prime Minister's advisors "made it clear that they are looking to cut a deal that gives them just enough to persuade enough voters to vote to stay in."
He added: "Once I realised that, my position in the Conservative Party became untenable."
The Prime Minister didn't seem to have any idea that this defection was coming. In interviews his shock was clear - just showing how out of touch he is with his own backbenchers. He said: "It's obviously deeply regrettable when things happen like this, when people behave in this way."
"But it's also, in my view, counter-productive. If you want a referendum on Britain's future in the EU - whether we should stay or go - the only way to get that is to have a Conservative government after the next election."
After dismissing the defection as counter-productive, the Prime Minister then went on to say, "the by-election in Clacton will be held as soon as possible" and that he "wants to make sure there's a very strong Conservative campaign in that seat."
At the time of writing, I think the Prime Minister sees this as a pertinent opportunity to shoot the UKIP fox. Essentially, he needs to put a strong Eurosceptic candidate against Douglas Carswell to stand any chance of overturning the former Tory MP’s 12,000 majority. And even that may not be remotely enough.
Carswell's decision will encourage many other brazenly Eurosceptic MPs to harden their rhetoric and stance on a referendum. This will also make things very interesting for swing voters worried about the cost of living and jobs. They will hear the Conservatives - to use the Prime Minister's words - "banging on about Europe".
This by-election presents Nigel Farage and UKIP with a distinct and ripe opportunity. Farage shared a platform with Carswell when the announcement was made, before a packed auditorium. This is the opportunity to prove, if the party hasn’t already, that it has the potential to rock the crumbling vessel of the political establishment.
Mr Farage said Carswell’s decision was "the bravest and most honourable" he had seen in modern British politics.
It was indeed a remarkably noble decision, and one that represents the stark new alternative UKIP offers to a disillusioned electorate.
Indeed, if the Warsi resignation didn’t prompt warning sirens in Mr Cameron's ears, this has to wake him up.
By Sean Mallis