A short follow-up to the post on Nick Clegg’s electoral surge in the UK. In the event of a hung Parliament, everyone assumes that Clegg is going to demand a change to proportional representation in exchange for his party’s political support. Plausibly, the more seats that his party gets, the more likely it is that Labour (the Liberal Democrats’ most probable coalition partner), will have an incentive to want PR itself, regardless or not of whether it wants Clegg’s support. The reason is straightforward. Duverger’s Law suggests that electoral systems like the UK’s have a strong tendency to lead to alternation between two major parties. Labour became one of those parties a century or so ago, replacing the Liberals (the organizational ancestor of the Lib Dems). The Liberal Democrats have been gaining ground over the last few election cycles, and may (if the polls bear out) win their biggest share of the vote since the 1920s. This _could_ be interpreted by nervous Labour MPs as possibly presaging a switch back to a system in which the Liberals and Conservatives dominate (I emphasize the word _could_ – this is likely to be a background fear rather than a worry in the foreground of their minds). In such a world, Labour would be better off in a system with proportional representation. In the rather implausible extreme of a significant lead for the Lib Dems and the prospect of becoming a genuinely national party, you could even see the Liberal Democrats deciding that they were better off under first-past-the-post than proportional representation – but this would be a very difficult u-turn to make under the best of circumstances. I’m not suggesting that this is likely to be a major factor – but in the event of a hung Parliament, and more-or-less equal shares of the votes for all the parties – it is a possibility that at least will loom in the background of any negotiations over government formation.