This review supports the following conclusions. First, the seminal decisions, which dominated deference doctrine for forty years, do not support a strong, highly deferential application of Chevron. To the contrary, the granting of deference prior to Chevron consistently depended upon the practical, common-sense considerations reflected in multifactor analysis. Second, the four decades before Chevron saw a shift in which political conservatives turned from Opposing to embracing heightened deference, while political liberals similarly reversed their positions from support to skepticism of deference. Third, Chevron itself is entirely consistent with previous deference doctrine. It does not support the "strong" reading urged by some commentators. Fourth, the multifactor or sliding scale analysis, which derives directly from the practical reasons for deferring to'agency interpretations, remains important to deference doctrine in the Sup;reme Court. Fifth, the current split on the Supreme Court over deference doctrine reflects an ideological division between liberals and conservatives, with liberals adhering to traditional deference analysis, while conservatives seek to impose strict limitations on judicial review of agency interpretations. The conservative effort, if successful, could have dramatic implications for the future of the administrative state.