  The addition of new multiplets of fermions charged under the Standard Model
gauge group is investigated, with the aim of identifying a possible dark matter
candidate. These fermions are charged under $SU(2)\times U(1)$, and their
quantum numbers are determined by requiring all new particles to obtain masses
via Yukawa couplings and all triangle anomalies to cancel as in the Standard
Model; more than one multiplet is required and we refer to such a set of these
multiplets as a polyplet. For sufficiently large multiplets, the stability of
the dark matter candidate is ensured by an accidental symmetry; for clarity,
however, we introduce a model with a particularly simple polyplet structure and
stabilize the dark matter by imposing a new discrete symmetry. We then explore
the features of this model; constraints from colliders, electroweak precision
measurements, the dark matter relic density, and direct detection experiments
are considered. We find that the model can accommodate a viable dark matter
candidate for large Higgs boson masses; for $m_H\sim 125$ GeV, a subdominant
contribution to the dark matter relic density can be achieved.
