Resuscitation of minimal SO(10) grand unification

It has been claimed that the minimal (nonsupersymmetric) SO(10) grand unified theory, with a single breaking scale $M_U$, is ruled out by the measurements of the standard-model gauge couplings at the $Z^0$ mass, and by the nonobservation of proton decay. We argue here that, if the threshold effects are taken into account, that theory is still quite satisfactory. We present an example in which the masses of all superheavy particles differ from $M_U$ by at most a factor of 10. Our picture of SO(10) breaking requires the rate of proton decay to be close to the present experimental limit.