In this chapter I introduce David Hume’s views on what I call, ‘affective leadership.’ By this I mean the political management of dispositions and emotions conducive to minimal union in the social-political sense. I present Hume’s ideas on this by way of close scrutiny of his (and Spinoza’s) extended treatment of the fall of the Dutch statesman, Johan de Witt. I do so in order to begin to articulate some distinctive features of a ‘Humean’ political theory in which the management of dispositions and emotions of a “spirit of union” play a central role. For De Witt is both praised for getting something truly right about the art of ruling, that is, to maintain the dispositions conducive to political unity, and also for getting something disastrously wrong, mistakenly assuming a species of rational behavior in others and thereby misunderstanding international politics, which is (also) governed by emotions. I show that such unity is possible for Hume as a consequence of the workings of Humean imitative sympathy.