The Ecology of Tactical Voting in Britain

Analyses of both aggregate-level constituency data and individual-level survey data from the 1983–2005 British General Elections indicate that when available information clearly signals which parties in a constituency are viable and which are not, supporters of nonviable parties vote tactically. Alliance/Liberal Democrat tactical voters tend to split their votes between Labour and the Conservatives, so the major parties derive limited net benefit from them. When Labour faces a dismal outlook in a constituency many of its supporters also vote tactically, and those that do overwhelmingly cast their votes for the Alliance/Liberal Democrats. Strong tactical support received from Labour voters has furnished the margin of victory in as many as a fifth of the contests that the Alliance/Liberal Democrats have won. A party that has repeatedly seen Duverger's mechanical” factor reduce the sizable share of votes it wins nationally to a far smaller share of seats thus turns out to be the biggest beneficiary of tactical voting