“…One approach actually explaining why influence occurs is the common agency or menu auction model of Bernheim and Whinston (1986), which got widely applied through the influential work of Helpman (1994, 2001). Applications of the model concern international trade policies Helpman 1994, 1995), electoral competition Helpman 1996, Prat 2000), Interestingly, Grossman and Helpman (1996) demonstrate that the function maximized by the policymaker can be endogenously obtained in an electoral competition model where parties maximize their seat shares in a legislature and where contributions can influence 14 Bernheim and Whinston (1986) show that the set of best responses to any strategies played by opponents includes a strategy that is 'truthful', which means that it reflects the true preferences of the interest group; moreover, such equilibria are 'coalition proof', in the sense that players cannot improve their lot through costless pre-play communication which carries no commitment.…”