  We study classically scale invariant models in which the Standard Model Higgs
mass term is replaced in the Lagrangian by a Higgs portal coupling to a complex
scalar field of a dark sector. We focus on models that are weakly coupled with
the quartic scalar couplings nearly vanishing at the Planck scale. The dark
sector contains fermions and scalars charged under dark SU(2) x U(1) gauge
interactions. Radiative breaking of the dark gauge group triggers electroweak
symmetry breaking through the Higgs portal coupling. Requiring both a Higgs
boson mass of 125.5 GeV and stability of the Higgs potential up to the Planck
scale implies that the radiative breaking of the dark gauge group occurs at the
TeV scale. We present a particular model which features a long-range abelian
dark force. The dominant dark matter component is neutral dark fermions, with
the correct thermal relic abundance, and in reach of future direct detection
experiments. The model also has lighter stable dark fermions charged under the
dark force, with observable effects on galactic-scale structure. Collider
signatures include a dark sector scalar boson with mass < 250 GeV that decays
through mixing with the Higgs boson, and can be detected at the LHC. The Higgs
boson, as well as the new scalar, may have significant invisible decays into
dark sector particles.
