  Understanding the process by which the individuals of a society make up their
minds and reach opinions about different issues can be of fundamental
importance. In this work we propose an idealized model for competitive cluster
growth in complex networks. Each cluster can be thought as a fraction of a
community that shares some common opinion. Our results show that the cluster
size distribution depends on the particular choice for the topology of the
network of contacts among the agents. As an application, we show that the
cluster size distributions obtained when the growth process is performed on
hierarchical networks, e.g., the Apollonian network, have a scaling form
similar to what has been observed for the distribution of number of votes in an
electoral process. We suggest that this similarity is due to the fact that
social networks involved in the electoral process may also posses an
underlining hierarchical structure.
