The Rainbow Parliament: The Commons will soon contain many more political hues, but our electoral system is pitifully ill-suited to reflect them

British by-elections sometimes become collector’s items – “earthquakes” that “break the mould” of politics, leaving “all bets off”, in the usual riot of mixed clichés they often induce.

Is Rochester such a collectable?

In some ways it was a less than classic performance from Ukip. Its winning margin was smaller than in Clacton, though it again had the advantage of an incumbent. A 7 per cent lead is not something that Mark Reckless should feel entirely comfortable with; it is not an impossible task for the Tories to win it back. Indeed, were it not for Emily Thornberry’s tweet ridiculing “White Van Man”, Labour might have been in with a chance of taking the seat Bob Marshall-Andrews held for 13 years after 1997.

On the other hand, when the by-election was called David Cameron unwisely declared that he would stop Ukip in its tracks. Had he managed to do so, the coverage would have been far less positive for Nigel Farage, and some early obituaries of his grand political adventure would be being published this weekend.

So the Ukip win in Rochester and Strood should be kept in perspective. One striking feature is the way that the vote share enjoyed by the three main parties collapsed in roughly the same degree; Labour down 12 percentage points, the Conservatives down 14, and the Liberal Democrats by 15. Of course, in the case of the Lib Dems that was virtually their entire vote, and left them behind the Greens and just ahead of the Monster Raving Loonies. This is not a great place to be for any of the three mainstream parties; Ukip is a problem for all of them.

That protest vote should sustain it between now and the election, the product of deep disillusionment with politics. But there were hints at the end of the campaign that Ukip has its own vulnerabilities. When Mr Reckless apparently called for EU migrants to be deported it raised eyebrows even in Ukip, and a “clarification” was swiftly issued. It gave an obvious clue to what Mr Cameron, Ed Miliband and Nick Clegg should do about Ukip – attack it relentlessly on the, admittedly often non-existent, detail of its policies. How would it reduce the deficit? Fund the NHS? Create jobs? Counter Islamic extremism? What would a new free trade treaty with the EU look like?

Still, Ukip will probably garner 10 to 20 per cent of the popular vote next year. The Lib Dems, if they are lucky, will drag themselves back up to that sort of level – itself poor by the standards of the past 20 years or so. The Greens will grab a better result than many have predicted, and the SNP will continue to make inroads into Labour’s Scottish core. Meanwhile, the public will remain stubbornly out of love with Mr Cameron and Mr Miliband.

The upshot is that next year a multi-hued House of Commons will be more fragmented than at any time since universal suffrage. Neither Tories nor Labour will find it easy to form a government, and, to use a much overused phrase, it will become obvious that the current electoral system is not “fit for purpose”.

The British electorate, collectively, is telling its rulers that it doesn’t like the way politics has been played, and that it wants more choice. It ought to be allowed to exercise that choice through a rational system that is much more proportional. That would remove the random nature of the present system, and offer something new. The next parliament has important work to do; not least reducing the deficit in a fair manner. It cannot work without reform.