  A reliable comparison of different dark matter (DM) searches requires models
that satisfy certain consistency requirements like gauge invariance and
perturbative unitarity. As a well-motivated example, we study two-mediator DM
(2MDM). The model is based on a spontaneously broken $U(1)'$ gauge symmetry and
contains a Majorana DM particle as well as two $s$-channel mediators, one
vector (the $Z'$) and one scalar (the dark Higgs). We perform a global scan
over the parameters of the model assuming that the DM relic density is obtained
by thermal freeze-out in the early Universe and imposing a large set of
constraints: direct and indirect DM searches, monojet, dijet and dilepton
searches at colliders, Higgs observables, electroweak precision tests and
perturbative unitarity. We conclude that thermal DM is only allowed either
close to an $s$-channel resonance or if at least one mediator is lighter than
the DM particle. In these cases a thermal DM abundance can be obtained although
DM couplings to the Standard Model are tiny. Interestingly, we find that
vector-mediated DM-nucleon scattering leads to relevant constraints despite the
velocity-suppressed cross section, and that indirect detection can be important
if DM annihilations into both mediators are kinematically allowed.
