  Switching from one electoral system to another one is frequently criticized
by the opposition and is viewed as a means for the ruling party to stay in
power. In particular, when the new electoral system is a parallel voting (or a
single-member district) system, the ruling party is usually suspected of a
biased way of partitioning the state into electoral districts such that based
on a priori knowledge it has more chances to win in a maximum possible number
of districts. In this paper, we propose a new methodology for deciding whether
a particular party benefits from a given districting map under a parallel
voting system. As a part of our methodology, we formulate and solve several
gerrymandering problems. We showcased the application of our approach to the
Moldovan parliamentary elections of 2019. Our results suggest that contrary to
the arguments of previous studies, there is no clear evidence to consider that
the districting map used in those elections was unfair.
