Party, constituency, and representation: Votes on abortion in the British House of Commons

To whom do British Members of Parliament respond when voting in the House of Commons? Using a series of votes on abortion, the revealed preferences of MPs are estimated. The results indicate that constituency characteristics matter, but they also underline the central importance of party. Even when discipline is not imposed, the Members of the three largest parties are distinct from one another. Moreover, there is a noteworthy interaction between constituency and party: the more marginal the seat, the more extreme the position. Members appear to react to electoral threat by reinforcing partisan bona fides with their local party rather than conforming to the median, recognizing the importance of partisanship for electoral success and the role of local party resources.