John Curtice: Scottish experience proves PR doesn't mean instability

THE Liberal Democrat surge has given the debate about electoral reform for the House of Commons a prominence it has not had for some 20 years. This is because it has helped uncover two questionable features of the current first-past-the-post system.

First, it appears the Liberal Democrats could still come a poor third in seats even if the party were to come second in votes. At the same time Labour might apparently be able to come first in seats, despite running third in votes. Such a possibility certainly does not make intuitive sense.

None of this should come as a shock to voters in Scotland, After all at the last Holyrood election, Labour won an overall majority of the first-past-the-post constituency seats even though the party was somewhat behind the SNP in votes.

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At the 1997 general election the Liberal Democrats came second in seats north of the Border, even though they were clearly fourth in votes.

Still, more generally the Liberal Democrats are the big losers under the current system. South of the Border, at least, their vote is geographically too evenly spread.

As a result even when they do well, they are at risk of coming second in lots of seats, but first in relatively few.

Even with the 30 per cent or so support they currently enjoy in the polls, the Liberal Democrats might still secure no more than 100 or so seats, just 15 per cent of the total. Any reasonably effective system of proportional representation – whether something like the current Holyrood additional member system or the single transferable vote used in Scottish local elections – would ensure they obtained more like 200 rather than 100 seats.

Perhaps just as importantly even if the Liberal Democrats were to fall back a level of support more typical for them in recent years – around 20 per cent or so – they might still, depending on exactly how proportional the system was, win between 100 and 150 seats in any general election.

Meanwhile, the ability of Labour under the current system to win more seats than the Conservatives, despite having fewer votes, would probably be eroded significantly too, albeit depending on the details of whatever alternative were introduced.

North of the Border, the SNP would expect to profit from reform. Even on the disappointing 18 per cent of the vote they won in 2005, they would win ten or so seats rather than the six they actually won, though they would still be small players in the Westminster game.

Most importantly, however, given that no British party has even come close to winning 50 per cent of the popular vote in recent years, hung parliaments would become the norm rather than the exception under a system of proportional representation.

With their large phalanx of MPs, the Liberal Democrats would potentially be perpetual kingmakers.

As a result Westminster politics would become more like that at Holyrood – a sequence of coalition or minority governments. Not everybody's cup of tea perhaps, but Scotland's experience suggests that at least it need not necessarily mean unstable government.

• John Curtice is professor of politics, Strathclyde University