  We use numerical simulations to study a formation scenario for dwarf
spheroidal galaxies in which their stellar populations are the products of the
dissolution of open star clusters and stellar associations within cosmological
dark matter haloes. This paper shows that this process gives rise to objects
which resemble the observed dwarf spheroidal satellites of the Milky Way
without invoking external influences. The presence of long-lived kinematic
substructures within the stellar components of these objects affects their
projected velocity dispersions. We find that this in turn affects mass
estimates based on the projected velocity dispersion profiles which may
over-estimate the actual dark matter halo mass depending on the amount of
substructure which is present. Our models make predictions about the detailed
kinematic and photometric properties of the dSphs which can be tested using
future observations.
