  Motivated by the realizability problem for principal tropical divisors with a
fixed ramification profile, we explore the tropical geometry of the double
ramification locus in $\mathcal{M}_{g,n}$.There are two ways to define a
tropical analogue of the double ramification locus: one as a locus of principal
divisors, the other as a locus of finite effective ramified covers of a tree.
We show that both loci admit a structure of a generalized cone complex in
$M_{g,n}^{trop}$, with the latter contained in the former. We prove that the
locus of principal divisors has cones of codimension zero in $M_{g,n}^{trop}$,
while the locus of ramified covers has the expected codimension $g$. This
solves the deformation-theoretic part of the realizability problem for
principal divisors, reducing it to the so-called Hurwitz existence problem for
covers of a fixed ramification type.
