  In this paper we analyze the asymptotic behavior of Cardassian cosmological
models filled with a perfect fluid and a scalar field with an exponential
potential. Cardassian cosmologies arise from modifications of the Friedmann
equation, and among the different proposals within that framework we will
choose those of the form $3H^2-\rho\propto \rho^n$ with $n<1$. We construct two
three dimensional dynamical systems arising from the evolution equations,
respectively adapted for studying the high and low energy limits. Using
standard dynamical systems techniques we find the fixed points and characterize
the solutions they represent. We pay especial attention to the properties
inherent to the modifications and compare with the (standard) unmodified
scenario. Among other interesting results, we find there are no late-time
tracking attractors.
