  We show that exactly marginal operators of Supersymmetric Conformal Field
Theories (SCFTs) with four supercharges cannot obtain a vacuum expectation
value at a generic point on the conformal manifold. Exactly marginal operators
are therefore nilpotent in the chiral ring. This allows us to associate an
integer to the conformal manifold, which we call the nilpotency index of the
conformal manifold. We discuss several examples in diverse dimensions where we
demonstrate these facts and compute the nilpotency index.
