We calculate the electrostatic persistence length l(e) both for flexible and for stiff polyelectrolytes using a self-consistent variational theory. For the case of intrinsically rigid polyelectrolytes we recover the classical results due to Odijk, Skolnick, and Fixman (OSF), namely, l(e) proportional to kappa(-2) where kappa(-1) is the Debye screening length. In contrast, l(e) for intrinsically flexible polyelectrolytes is found to be proportional to kappa(-1) in the limit of large screening. This is in accord with simulations, experiments, and numerical estimates. We also provide a criterion for the crossover from the OSF result to the behavior observed for intrinsically flexible polyelectrolytes.