What causes politicians to vote against their parties’ wishes? What causes parties to exhibit less or greater discipline? How do institutions influence the way legislatures, parties and parliament members behave? The researcher wants to undertake 2 related tasks: first of all, the researcher wishes to add to our knowledge about the effect of institutional arrangements on parties and parliament members by shedding light on an often neglected institution: parliamentary cameral procedures. The second objective of this research is to innovatively examine how the combination of political institutions, and specifically electoral systems, intra-party candidate selection processes and parliamentary cameral procedures, and their interaction with one another influence the way legislators’ behave and the degree to which parties are acting in unison. I aim to investigate the nature of the relationships between political institutions and politicians’ behaviour, in order to improve theory and help practitioners in designing institutions, which lead to better political representation and greater democratic stability. Both tasks are valuable for the advancement of the study of legislative behavior and parties. In its core the project seek to answer how do the institutional arrangements within which legislators and parties operate shape and influence their behavior?