Behavioral paternalists often distinguish their views from harder forms of paternalism by emphasizing the moderate character of their proposals. Insights from the academic literature on slippery slopes suggest that behavioral paternalist policies are particularly vulnerable to expansion, which makes the claim to moderation unsustainable. This is true even if policymakers are rational (in the neoclassical sense), but the slippery-slope threat is even greater if policymakers share the behavioral and cognitive biases attributed to the people their policies are supposed to help. Rational slope mechanisms include altered incentive slopes, authority and simplification slopes, and expanding justification slopes. Behavioral slope mechanisms include action bias, overconfidence, confirmation bias, present bias, availability and salience effects, framing and extremeness aversion, and affect and prototype heuristics. The theoretical and empirical vagueness of behavioral paternalism creates gradients that encourage the gradual expansion of policies. Finally, the particular way in which leading behavioral paternalists have framed the issue of paternalism gives rise to an inherently expansionist dynamic, which we call the paternalism-generating framework.