Electoral Anti-Corruption Law... Looks Good
Realizing the Venice merchant families are corrupting the elections, a complex lottery is adopted to select the people who will elect a city manager. In ten rounds of voting, a voting committee selects the members of a second voting committee which in turn selects a third voting committee... etc, etc, ... until a final committee votes to elect a Doge to run the city.
The title "Doge" suggests a military commander but the Doge will be severely limited in power. 
Massive Death Toll
A massive earthquake in what is today southern Turkey kills 60,000 people. While this is a large death toll in any age, the world population is around 120 million. If a similar proportion of the world population were killed TODAY, assuming 7.13 billion world population, would be 3,565,000 dead...in a day or two. 
No New Pope
Pope Clement IV is dead, but it will take three years to elect another Pope. The Vatican controls a large military force. To be leaderless for so long will be a significant lapse. 
France Hops on New Beer Law
- "Electing the Doge of Venice: analysis of a 13th Century protocol" by Miranda Mowbray, Dieter Gollmann, 2007. (PDF)
- 1268 - Wikipedia
- "18-year-old pope, three-year election: Quirky facts about papal conclaves", originally from Associated Press, March 11, 2013
- "The Oxford Companion to Beer", edited by Garrett Oliver, Oxford University Press, 2012, p. 464.
- "Hops: the Bitter Herb", summarized by Master Rhys Terafan Greydragon from various sources listed on his site