Who Is Watching Tonight?

Partisans mostly:

In general, political scientists find that the biggest effect of major campaign events is to activate partisan predispositions. The campaign as a whole has this result, but the effect may be even more dominant for conventions and debates that require one to self-select to be a viewer. This activation effect is driven by that fact that those most interested in politics are also the most likely to have strong existing views (see here and here). A very large portion of those who tune in are political junkies/activists who made up their minds long ago or those who are at least partisan enough that watching these events reminds them what they like about their party and dislike about the other one.