Some of its critics complain that UKIP is the real Nasty Party, but we Conservatives should be wary of deploying the claim – after all, it has unfairly hurled at us ever since Theresa May was unwise enough to coin it.  I’m sure there are some very nice people in UKIP.  But are there any cheerful ones?

The party’s voters are “older and poorer than the national average. Many feel that the modern world has left them behind. They want to return to the days when Britain was quieter, whiter, more predictable and less European,” as Peter Kellner of YouGov put it.  This view is broadly backed up by many others – including Rob Ford and Matthew Goodwin, authors of what remains the standard guide to the party.

Whatever else may be said of Douglas Carswell, he doesn’t lack good cheer.  He is so hopeful about Britain, the world, and the future that optimism simply shines out of him – in the enthusiasm for direct democracy, new technology, and constitutional reform that long predates his defection to UKIP.

This helps to explain why he has frequently gone public to argue that the party must change – especially when it comes to attitudes to immigrants.  “Far from being a party that tolerates pejorative comments about people’s heritage and background, UKIP in 2015 has to show that we have a serious internationalist agenda”, he wrote last year. “No UKIP candidate should ever make the mistake of blaming outsiders for the failings of political insiders in Westminster.”

It is thus a difference not so much of policy but of outlook that has marked the Clacton MP’s relationship with UKIP ever since…well, pretty much ever since he has joined it – exemplified in his refusals to be drawn over Nigel Farage’s views on HIV, immigrants and the NHS.

Mark Wallace has chronicled some of the tensions on this site, describing the Carswell tendency within the party as “Bright Purple UKIP“.  The row between the Clacton MP and UKIP staffers over Short Money is only the latest difficulty – throwing into harsh relief the difference between the culture of Janice Atkinson, whose staff inflated a restaurant bill, and that of Carswell himself, “the sea-green incorruptible”.

When the Clacton MP left the Conservatives for UKIP, I wrote that the party’s “opportunist bandwagon is unworthy of him – and suspect that he may swiftly find this out”.  The learning process seems to be well underway.  Carswell is a happy man, but is he really happy with the party he’s joined?