Previous research on the impact of reforms to the Portuguese electoral system has assessed
mechanical effects assuming that the behavior of individuals would remain the same. We
improve on this state of affairs by using a rich dataset to study the impact of district
magnitude on three relevant decisions made by individuals: the decision to vote or abstain,
the decision to vote sincerely or not and the party choice decision. Then, we use our models
to predict the effects of four alternative scenarios: uniform-size circles, a reduction of
Members of Parliament to 180, a national circle and single-member circles. Besides making
contributions to the understanding of how several individual and contextual-level variables
shape the voting behavior of the Portuguese, we make four additional contributions in
this study. Firstly, we show that the relationship between district magnitude and the
probability of abstention is negative and shows diminishing returns. Secondly, we show
that the impact of district magnitude on the probability of voting strategically is strikingly
similar to its impact on the probability of abstaining. Thirdly, we show that district
magnitude plays an important role in shaping the choice of party by individuals. Finally,
by using the models estimated we quantify the impact of different types of redistricting
on abstention, sincere voting and party choice
