Using MP statements to explain voting behaviour in the German Bundestag : An individual level test of the Competing Principals Theory

Why do members of parliament (MPs) vote against the party line? Recent explanations of party unity focus on MPs crosspressured between the demands of competing principals such as their party and local constituencies. This article tests key claims of the Competing Principals Theory on the level of individual deputies. It relies on public statements in which MPs explain their voting behaviour. This new data source allows more direct insights into MPs’ decision-making calculus than roll-call data. The article develops a theoretical model for the usage of such statements and the position MPs take vis-à-vis the party line. Empirically, it studies Explanations of Votes on all roll-call votes in the 16th German Bundestag (2005–2009) statistically controlling for sample selection. The analyses show among others things that district MPs take more critical stances, party leaders dissent less and government MPs are more likely to voice reservations without defecting in voting.