Why were some Arab countries deeply affected by the Arab Spring, while others were ‎not? I make three arguments in this paper. First, it was very quickly apparent how serious ‎the protests would be in each Arab country (except Syria), and the speed of diffusion ‎suggests that regime reactions were much less important than citizen attitudes toward the ‎regimes on the eve of Ben Ali's fall from power. Second, in the initial burst of diffusion, all ‎Arab regimes looked vulnerable. Having lost their aura of invincibility, citizens demanded ‎the fall of the regime in countries in which that demand had a strong appeal to a wide ‎section of the citizenry. This was not the case in most Arab countries. Third, the decision by ‎citizens to demand the fall of the regime (or not) can best be explained by a set of political ‎factors, one of which is a preference in Arab public opinion for the reform, rather than the ‎overthrow, of monarchies. In making these arguments I draw on the lessons of the ‎literature on the diffusion of similar revolutionary shocks, especially the revolutions of 1848 ‎and the Color Revolutions in post-Communist states in the 2000s. ‎