Spatial variations in voter choice: modelling tactical voting at the 1997 general election in Great Britain

Tactical voting, whereby electors vote for their second-choice rather than their first-choice party, in order to unseat an unpopular incumbent, has been pressed at recent British general elections; the supporters of the opposition Labour and Liberal Democrat parties strove to remove the Conservative government. It appeared to succeed at the 1997 general election. To establish whether this was the case we modelled: (a) the pattern of voting at the previous general election - necessary because of a redistricting since; (b) the gross inter-party flow-of-the-vote in every constituency; and (c) the expected pattern of tactical voting, given the marginality of constituencies, the relative chances of success for the two opposition parties in each Conservative-held seat and the parties' local campaign strategies. Tests of the third model provide strong evidence that tactical voting did occur, and that its intensity was closely associated with party campaign effort.