  In a signed graph, each link is labeled with either a positive or a negative
sign. This is particularly appropriate to model polarized systems. Such a graph
can be characterized through the notion of structural balance, which relies on
the partitioning of the graph into internally solidary but mutually hostile
subgroups. In this work, we show that signed graphs can be used to model and
understand voting behavior. We take advantage of data from the European
Parliament to confront two variants of structural balance, and illustrate how
their use can help better understanding the studied system.
