Alternative Vote change would boost Lib Dems
Labour's proposed reform to the voting system for the House of Commons, the so-called Alternative Vote, would, in current circumstances, prove just as ineffective at reflecting the order of the parties as the existing system.
A latest poll puts the Conservatives first on 32%, just ahead of the Liberal Democrats on 31%, while Labour are behind in third place with 28%.
However, under the current system such a result would probably mean Labour would come first in seats with a tally of 268, the Conservatives second with 238, while the Liberal Democrats would clearly be third with just 112. The Liberal Democrats would lose out so badly because their votes are geographically too evenly spread.
Labour do so well because Labour-held seats on average contain smaller electorates, a feature compounded by the fact that turnout tends to be lower in the party's strongholds.
Under the Alternative Vote the Liberal Democrats would fare much better. Under this system voters place candidates in rank order — 1, 2, 3 and so on. If no candidate wins 50% of the first-preference vote, then the votes of candidates at the bottom of the poll are redistributed in accordance with those voters' second preferences, and so on, until someone passes the 50% mark.
Nick Clegg's party tends to be everyone's second choice. As many as 68% of Labour supporters say they would give a second-preference vote to the Liberal Democrats, as do 41% of Conservatives.
So if the Liberal Democrats are running second in a constituency, they can hope to leapfrog into first place on the back of second preferences cast by third-placed Conservative or Labour supporters.
The party might win up to twice as many seats — 217 — as they would under the current system.
John Curtice is professor of politics at the University of Strathclyde