  We accurately approximate the contribution that photons make to the effective
potential of a charged inflaton for inflationary geometries with an arbitrary
first slow roll parameter $\epsilon$. We find a small, nonlocal contribution
and a numerically larger, local part. The local part involves first and second
derivatives of $\epsilon$, coming exclusively from the constrained part of the
electromagnetic field which carries the long range interaction. This causes the
effective potential induced by electromagnetism to respond more strongly to
geometrical evolution than for either scalars, which have no derivatives, or
spin one half particles, which have only one derivative. For $\epsilon = 0$ our
final result agrees with that of Allen on de Sitter background, while the flat
space limit agrees with the classic result of Coleman and Weinberg.
