Toward A Political Explanation of Government Vote Losses in Midterm By-Elections

By-elections in parliamentary democracies are remarkable for the almost invariable loss of support experienced by governments relative to the preceding general election. There has been, however, surprisingly little research into this phenomenon. Using Britain as a test case, this article goes some way towards filling this gap. It identifies and tests three political explanations of governments' by-election vote losses, which it labels the turnout, referendum and personal vote models. No simple conclusion emerges, since different results are obtained depending on whether the models are treated as separate entities or their interplay is taken into account by integrating them into a single causal model. This latter strategy is argued to involve a superior conceptualization of the processes at work in bringing about governments' midterm vote losses.