Ukip's success in yesterday's by-elections poses a question for the left: why has disquiet with the Establishment led to support for a rightist party rather than the left?

It would be wrong to dismiss Ukip voters as merely racist. For one thing, their massive support for public ownership of utilities puts them to the left of Labour. And for another, as Matthew Goodwin has pointed out, they are reacting against being neglected by the main parties; on this, even Richard and Frances agree.

On both grounds, the Left could mobilize such voters. But it hasn't. Why?

You might reply that it's normal for meanspiritedness and racism to increase in hard times and Ukip are tapping into this. But this just relocates the question: why have we failed to prevent such atavistic instincts gaining political expression? The question gains force because there's a strong rational argument against anti-immigrationism:

- The evidence (pdf) shows that immigration actually increases jobs and wages - perhaps even of the worst off.

- There are many bigger threats to the living standards of the sort of less educated people attracted to Ukip such as power-biased technical change, deindustrialization, globalization (pdf) and secular stagnation. A politics that was seriously concerned for the worst off would address these issues, rather than treat migrants as a threat.

- Even if we were to concede that immigrants are a threat to some British workers, the solution is not immigration controls - because if foreign workers stayed at home they'd depress UK wages through trade. Instead, the answer is some mix of jobs guarantee, expansionary macro policy, stronger trades unions and a citizens' basic income.

So, why have these arguments so little force with voters? Is it because the Left hasn't been brave enough to make them? Or because they are wrong? Or because the Left lacks a decent platform to do so and is shouted out by the media?

You might reply that I'm missing the point, and that disquiet with immigration is because people feel "uncomfortable" traveling on a bus or a train where nobody speaks English. This, though, poses other questions: if this is so, why do relatively few people say immigration is a problem in their own area (p90 of this pdf), and how come Ukip did so well in Clacton, which has so few immigrants? Do such people also feel uncomfortable watching Ola Jordan and Kristina Rihanoff on Strictly Come Dancing? And why has a non-economic feeling become so strong at a time of hardship?

Now, it certainly suits the Establishment for generalized discontent to be channelled into support for an anti-immigration party. It's no accident, therefore, that the media has emphasized anti-immigrationism and bigged up Ukip. But again, there's a question: why has the Left been so impotent in the face of this?

It's tempting to blame the power of the Establishment and the supineness of the Labour party. But are these really solely to blame? Or could it be instead that part of the fault lies also with the non-Labour Left itself, which is so congenitally disorganized that it couldn't pour piss out of a boot if the instructions were printed on ther heel?