Piñera and [Chile's] binomial system

Greg Weeks at Two Weeks Notice comments on the possibility that Chile’s president, Sebastian Piñera, may be joining the (growing?) bandwagon for electoral system reform in Chile.

It’s only inevitable, I suppose, that electoral system reform fever would reach Chile. I’m partly sad, because Chile’s binomial system—a platypus of an electoral system made for interesting teaching (as did Uruguay’s ley de lemas, or double simultaneous voting, system).

Obviously, the binomial system is just a holdover from the Pinochet era, when the outgoing dictatorship sought to safeguard its policies and virtually ensure a (slim) conservative majority. That system has outlived its use, and electoral volatility and voter antipathy is already eroding the party system tied to the binomial system, making it increasingly unwieldy. But what would replace it? And what would its effects be on the party system—and on governance—in Chile?

(I ask these questions with an eye to my INST 316 seminar on electoral systems and party systems, in which Chile is one of our case studies.)