The assumption is difficult to test, but analogies can be drawn with the impact of spending (which is capped) in the constituency campaigns. In our evidence to the House of Commons Home Affairs Committee inquiry into the funding of political parties, we reported on analyses of spending at the 1983, 1987 and 1992 general elections in the 633 British parliamentary constituencies. These showed significant statistical relationships between the amount spent by each party in a constituency and its percentage of the votes cast there: the more a party spent, the better its performance; the more its opponents spent, the worse its performance.
Furthermore, simulations suggested that if different amounts were spent, the result could have been significantly altered: in 1992, for example, if Labour had spent the maximum sum possible in each constituency, but the Conservative Party spending remained at the reported level, then Labour could have won 15 more seats.
Such statistical analyses do not 'prove' that campaign expenditure 'buys' votes, only that there is a relationship between the two. But they do provide strong circumstantial evidence that local campaign activity - including the expenditure of up to pounds 6,000 on advertising over a three- to four-week period - is a profitable investment of party funds.
R. J. JOHNSTON
(University of Essex)
C. J. PATTIE
(University of Nottingham)