The House of Commons has just voted 334-292 against plans to tweak Britain’s constituency boundaries. This is bad news for David Cameron, whose Conservative Party would have received a handy electoral fillip from the planned changes. But it is not unexpected. When a rebellion by 91 Conservative MPs forced the government to scrap plans for House of Lords reform last summer, Nick Clegg felt compelled to wallop the Tories in retribution, and withdrew his support for boundary change. His coalition partners, he complained, had not kept their side of the bargain. Tories recall no such deal. They have a point: Mr Clegg is on record denying any link between the two measures. But that’s coalition, folks.

Since then the proposed revisions to Britain's political map—painstakingly drafted by the Boundary Commission to iron out disparities in constituency size and cut the number of MPs from 650 to 600—have been a near-irrelevance. There are 303 Conservative MPs, 23 short of a Commons majority. Despite fanciful talk of a deal with small Northern Irish, Scottish and Welsh parties to make up the numbers, tonight’s vote was never likely to go the Tories’ way. In the event, four of their own number sided with Labour, the Lib Dems and the smaller parties, giving the No camp a surprisingly large majority of 42.

The vote is significant for several reasons:

  1. Most significantly, it lengthens the odds on a Conservative majority at the next election. Equalising constituency sizes would have helped to correct the bias against the party in the British political system—by at least 20 seats. Today’s defeat will intensify the party’s hunt for votes.
  2. It skewers the notion, popular on the Tory right, that the Conservatives could ditch the Lib Dems and form a viable minority government. However much they dislike their partners (and today’s vote does little to help), they need them.
  3. It widens the gap between Mr Cameron, who grudgingly tolerated Mr Clegg’s tit-for-tat sabotage, and Tory backbenchers, who are apoplectic.   
  4. It stresses the value of a rigorously-drafted coalition agreement. The 2010 deal, negotiated in conditions of sleep deprivation and media hysteria, was thrashed out in just five days. Today’s upset is rooted in unresolved ambiguities in that agreement.
  5. It accelerates the process of candidate selection. Recent elections have shown that candidates with time to establish themselves in their constituencies have a healthier chance of winning. The parties had started to pick candidates for the existing constituencies before this vote; now there is no risk of a shake-up, the process will gain pace.
  6. It nobbles a sensible political reform. Britain’s constituencies vary greatly in population, giving some voters a louder voice than others. Reshaping them, reducing the size of the Commons in the process, would have made Britain’s democracy leaner and fairer.
  7. It worsens relations between the two coalition parties, setting a precedent for future disagreements. And, with debates on Europe, press reform and the spring Budget looming large, it is only a matter of time until the next dust-up.