The value of making an extra effort: campaign spending and electoral outcomes in recent British General Elections -- a decomposition approach

An increasing volume of research has shown that the amount which British political parties spend on constituency campaigns at general elections is related to their relative performance there. Because parties are better able to mobilise campaign resources where they are already electorally strong, and because they tend to remain strong in the same parts of the country over long sequences of elections, however, there are technical problems in separating out the 'real' impacts of campaign spending from those which reflect prior strength. A two-stage modelling procedure is introduced here which allows such separation: it provides strong evidence that where parties spend more than the average for a constituency of a certain type, they garner electoral rewards accordingly.