  We present a simple kinetic model for the assembly of small single-stranded
RNA viruses that can be used to carry out analytical packaging contests between
different types of RNA molecules. The RNA selection mechanism is purely kinetic
and based on small differences between the assembly energy profiles. RNA
molecules that win these packaging contests are characterized by having a
minimum "Maximum Ladder Distance" and a maximum "Wrapping Number".The former is
a topological invariant that measures the "branchiness" of the genome molecule
while the latter measures the ability of the genome molecule to maximally
associate with the capsid proteins. The model can also be used study the
applicability of the theory of nucleation and growth to viral assembly, which
breaks down with increasing strength of the RNA-protein interaction.
