It's funny -and not counter to your point- but several of the succession struggles that plagued the Eastern Empire are characterized as "almost elections", by historians. Since its inception, the empire never had an official succession system and hence every new ruler was contested. Constantinople was so easily defendable that a popular usurper had great chances of making himself with the throne if he could take control of the capital. More than once, pretenders rose to power by popular acclaim at the hippodrome.