Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Boix. 1999. Setting the rules of the game: The choice of electoral systems in advanced democracies. American Political Science Review 93 (September): 609-24.
"Looking at the history of democracies in the developed world, I show that electoral systems derive from the decisions the ruling parties make to maximize their representation according to the following conditions. As long as the electoral arena does not change and the current electoral regime benefits the ruling parties, the electoral system is not altered. As the electoral arena changes (due to the entry of new voters or a change in voters' preferences), the ruling parties modify the electoral system, depending on the emergence of new parties and the coordinating capacities of the old parties. When the new parties are strong, the old parties shift from plurality/majority to proportional representation if no old party enjoys a dominant position, but they do not do this if there is a dominant old party. When new entrants are weak, a system of nonproportional representation is maintained, regardless of the structure of the old party system."
Current governing parties will keep the current electoral rules if they think doing so will maintain their power. If the current governing powers fear a decline in their influence, they will change to PR so that they can keep a voice even if they become a minority. More formally (but not formal theory), three sequential steps determine whether ruling parties will change the party system.
Boix's important contribution to studies of constitutional design is this: Rather than arguing about which constitutional design is "best" (as many comparativists do), he simply asks how our view of constitutional engineering changes when we acknolwedge that the engineers (i.e. politicians) are not benevolent planners. In essence, he assumes that elites know and accept Cox's (1997) logic, and then asks what elites would do with this knowledge.
Research on similar subjects