Jets from quasars and other active galactic nuclei can exceed their host galaxy in size and luminosity, yet their astrophysical mechanism remains obscure. More than four decades ago, Blandford and Znajek argued that the jets come from frame drag by the spin of a super-massive black hole. However, direct observational tests of this argument are lacking. Similarly, dark matter accounts for nearly one-third of the energy density of the universe and dominates the structure and evolution of galaxies and galaxy clusters, yet laboratory and accelerator searches have failed so far to directly detect and characterize dark matter candidate particles and fields. Remarkably, at the horizon of a spinning black hole, the electric and magnetic fields align near the poles to create precisely the configuration needed for the production of an intense beam of dark matter in the form of low mass, pseudo-scalar bosonic particles known as axions. The subsequent two-photon decay of axions in the dark matter beam would then provide an astrophysical mechanism for the jets from quasars and other active galactic nuclei. We propose using observations of jet spectra, luminosity, and polarization to test this mechanism and to probe the mass and coupling strength of dark matter in the form of axions.