Sliding-singlet mechanism revived

It is shown, using a modification of an idea of Sen, that completely realistic supersymmetric grand-unified theories based on $\mathrm{SU}\left(6\right)\mathrm{}$ or larger unitary groups can be constructed using the sliding-singlet mechanism. These models have a simple structure, preserve the successful prediction of ${\sin }^2{\theta }_W,$ and can suppress Higgsino-mediated proton decay to an acceptable level in a simple way.