It will be interesting to see how UKIP handles Carswell winning Clacton, as I expect him to do. Some restraint is needed because he was, after all, the sitting MP and not some 'unknown quantity'.
Perversely, them winning that seat at this juncture could be counter-productive to their overall aspirations to make inroads at the May 2015 General Election. Voters may see them gloating over getting their first MP as a sign that a simple protest vote might indeed usher in Labour, so could galvanise the casual Tory vote into action.
I'm hoping it will make a few more Tories defect.