It's about Farage, not Carswell.
The first obvious criticism to make when that rare thing, an MP resigning only to stand again in the subsequent by-election on a different platform or principle happens, is self-indulgence. This was thrown at David Davis when he stood down over 42 days detention, and clearly annoyed the Tory leadership despite Cameron just about managing to swallow his pride and campaign for the man he challenged for the leadership. To give Carswell some credit, he has long campaigned for political reform and the public recall of MPs, a perfectly reasonable measure but one I've always felt could be triggered too easily by single issue campaigners under the system proposed by those pushing for it.
All the same, to stand down and trigger a by-election now, when we are only about 8 months away from the general election doesn't exactly speak of concern for the public purse. Had he wanted to, Carswell could still have defected and hung on in his seat until the general election, then stand for UKIP. Indeed, it would probably give him the best possible chance of remaining the MP, seeing as he will now face two votes within the space of 8 months. He could easily win the by-election, only to lose his Clacton seat next year once the Tories have had time to build their candidate up in the constituency.
This isn't about Carswell though, it's about UKIP, Farage and keeping the party in the headlines right up until the election. Give the party's adviser Patrick O'Flynn his due, the former Express hack knows both how to time their announcements and how to keep the illusion of pressure up on the Tories. If making it the same day as the latest immigration figures were published wasn't coincidence, the rise of net migration to 243,000, just the 143,000 above the Tories' target, it couldn't have put their raison d'etre back on the agenda better. With the media still more than happy to fluff Farage, despite his anointment as candidate for South Thanet guaranteed weeks ago, you can't help but wonder whether the Liberal Democrats are going to be left struggling with the Greens for attention, at least until everyone remembers at best UKIP might, emphasis on the might, pick up 1 or 2 seats next May.
Nor should Carswell get re-elected will he be the first UKIP MP, considering Bob Spink's defection to the party in 2008. More important is proving Farage right in his prediction the party will pick up seats, or can win at least once, not having managed to do so in all the previous by-elections. The party must be fairly confident he can take his support with him, as losing would be a humiliation; recoverable from certainly, but the kind of setback Farage has previously said could "puncture their bubble".
The other motive presumably is to put the same idea in the heads of other Eurosceptic Tory MPs, suggesting they too could defect and still keep their seats, being as right-wing as in their dreams, supporting their former party on a case-by-case basis. It's why the Tories will throw as much at the campaign as they can, hoping they can make the best of a bad situation. As for Labour, it's a dream: the Tories tearing themselves apart over an issue the public are only exercised about by proxy. It will also split the vote in Clacton: unlikely as it is they could pick the seat up as a result, it will put under scrutiny the claim from both academics and UKIP alike that they pose as much of a threat to Labour. Interesting times, at least for us politics nerds, are ahead.
(P.S. There's a simple reason I'm not on Twitter, or Facebook for that matter. They're not for me. I really appreciate the kind words about yesterday's post nonetheless.)