  We present a model of voting behaviour based on a version of aggregated
overdispersed multinomial distributions; relative to a similar model by
\citet{BP86}, our model is based on more realistic assumptions and free from
certain shortcomings of the previous model. We show that, within this model, it
is possible to test for certain confounding effects due to observable
covariates measured at the aggregate level; such effects, if ignored, might
cause substantial bias in the estimated relation between voting decisions in
two close in time elections, a phenomenon known as {\em Ecological Fallacy}. An
application to a referendum following an election for the major in the town of
Milan, which was interpreted as a defeat for the Berlusconi gouvernment, is
used as an illustration.
