We prove a family of
identities connected to a divisibility property of the Kostant partition function. A
special case of these identities first appeared in a paper of Baldoni and Vergne. To
prove their identities, Baldoni and Vergne used residue techniques, and called the
resulting divisibility property “mysterious.” Our proofs are entirely combinatorial and
provide a natural explanation for why divisibility occurs, both in the Baldoni and
Vergne identities and in their generalizations.