Given the news that Pope Benedict XVI will resign at the end of this month, the first bishop of Rome to do so since the middle of the last millennium, the college of cardinals will soon convene to elect his successor.

Political scientists Forrest Maltzman, Melissa Schwartzberg, and Lee Sigelman researched how Pope John Paul II changed the papal constitution to force an outcome. As they wrote after Benedict’s selection in 2005,

Officially, Ratzinger’s selection was attributed to the will of God … The more immediate source of this outcome, however, was a factor about which political scientists can justifiably claim considerable expertise: the rules under which the election was held. Indeed, Pope John Paul II was certainly aware that these rules would shape the outcome of the election: otherwise there would have been no need for him to modify them.

As Maltzman, Schwartzberg, and Sigelman discuss, the papal constitution was reshaped in part because of the influence of consultant (and Nobel Prize winner) Kenneth J. Arrow, who helped shaped the Pontifical Academy’s voting rules to guarantee that the conclave could not be deadlocked.

Update: It turns out that since Benedict’s elevation, he has returned the papal elections to the traditional two-thirds margin. This could well result in a longer papal conclave than the last one (which was fast). For the Church, this could be a little bit of a problem, as a lengthy conclave during the Lenten season could leave the hierarchy without a Pope during Easter. Presumably, of course, Benedict’s move away from the Ken Arrow voting rules was also strategic; perhaps he feels confident that “his” man will be elected under a two-thirds rule. That could mean that the next pope is simply a younger, healthier, equally conservative Benedict supporter. (Thanks to Kevin Collins.)

Second Update: Josep Colomer and Iain McLean, “Electing Popes: Approval Balloting and Qualified-Majority Rule”, Journal of Interdisciplinary History (1998). A useful history of papal elections:

This article demonstrates that successive reforms in the rules for electing popes during the Middle Ages can be explained as a series of rational responses to political problems faced by the Church and by successive electors. Although the particular forms that these developments took could not have been predicted in advance, because they depended on certain contingencies (such as the unusual utility function of Celestine V), the process as a whole is illuminated from the perspective of social choice theory.

(Thanks to Kevin Collins.)

Update 3 Not peer reviewed but this undergrad research paper by Adam Brickley got the year of Benedict’s removal as pope right and has a neat-looking scorecard of potential papal successors. (Astonishingly, Brickley might have gotten Sarah Palin named VP candidate.

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