  We consider a theory of gauge fields and fermions which we argue gives rise
to dynamics similar to that of the Nambu--Jona-Lasinio (NJL) model when a gauge
coupling constant is appropriately fine-tuned. We discuss the application of
this model to dynamical electroweak symmetry breaking by a top-quark
condensate. In this model, custodial symmetry is violated solely by
perturbatively weak interactions, and the top--bottom mass splitting is due to
the enhanced sensitivity to custodial symmetry violation near the critical
point. We also consider models in which electroweak symmetry is broken by new
strongly- interacting fermions with NJL-like dynamics. We argue that these
models require additional fine-tuning in order to keep corrections to the
electroweak $\rho$-parameter acceptably small.
