Moral appeals – appeals to fundamental beliefs about right and wrong – have the potential to mobilize and persuade voters, as demonstrated in recent political science and moral psychology research. However, whether this potential means that politicians use moral appeals strategically has so far not been investigated. If this were the case, we should see moral appeals ebb and flow with the election cycle, such that moralization intensifies as an election is nearing. To test politicians’ strategic use of moral appeals, we use fine-grained social media data from six countries over an eight-year period to document dynamic changes in moralization including whether such changes can be predicted by distance to an election. We also examine the relative use of positive moral appeals emphasizing virtues and negative moral appeals emphasizing vices as a function of the election cycle. Finally, to validate the mobilizing potential of moral appeals, we examine patterns of likes and retweets, including whether moral appeals are more effective in generating social media engagement during election campaign periods. Our study holds important implications for understanding politicians’ strategic communication in a cross-national perspective.