  We report x-ray scattering studies of broad peaks located at a (0.5 0 0)/(0
0.5 0)-type wavevector in the paramagnetic insulating phases of
La_{0.7}Ca_{0.3}MnO_{3} and Pr_{0.7}Ca_{0.3}MnO_{3}. We interpret the
scattering in terms of correlated polarons and measure isotropic correlation
lengths of 1-2 lattice constants in both samples. Based on the wavevector and
correlation lengths, the correlated polarons are found to be consistent with
CE-type bipolarons. Differences in behavior between the samples arise as they
are cooled through their respective transition temperatures and become
ferromagnetic metallic (La_{0.7}Ca_{0.3}MnO_{3}) or charge and orbitally
ordered insulating (Pr_{0.7}Ca_{0.3}MnO_{3}). Since the primary difference
between the two samples is the trivalent cation size, these results illustrate
the robust nature of the correlated polarons to variations in the relative
strength of the electron-phonon coupling, and the sensitivity of the
low-temperature ground state to such variations.
