  Roughly speaking, gerrymandering is the systematic manipulation of the
boundaries of electoral districts to make a specific (political) party win as
many districts as possible. While typically studied from a geographical point
of view, addressing social network structures, the investigation of
gerrymandering over graphs was recently initiated by Cohen-Zemach et al. [AAMAS
2018]. Settling three open questions of Ito et al. [AAMAS 2019], we classify
the computational complexity of the NP-hard problem Gerrymandering over Graphs
when restricted to paths and trees. Our results, which are mostly of negative
nature (that is, worst-case hardness), in particular yield two complexity
dichotomies for trees. For instance, the problem is polynomial-time solvable
for two parties but becomes weakly NP-hard for three. Moreover, we show that
the problem remains NP-hard even when the input graph is a path.
