Using simple statistical mechanical models, we present a theory based on a free energy function that combines classical models of the helix-coil transition in polymers with approximate treatments of the effects of excluded volume, confinement, and helical packing. The theory includes local signals for folding in the form of stabilization energies for three types of local structure. Randomness in the energies of the conformational states is also considered. The thermal behavior of the model is presented for realistic estimates of the signal energies. Estimates of the relative contributions of local signals and specific tertiary interactions to the folding stability gap are obtained.