Wow. The Atlantic has a transcript of Bill Clinton's nominating speech that overlays the speech he actually gave atop the prepared remarks. At first, the differences are relatively restrained elaborations and intensifiers. When he gets into the heart of the attack on Republican positions -- themselves an attack on his entire legacy -- the green-shaded ad-libs swamp the prepared text.
When I first eyeballed those later sections, I thought, "My God, he ad-libbed all that detailed policy contrast -- the analysis of their Medicare and Medicaid proposals, the debunking of their welfare attacks." That isn't true, though. The factual nuggets are almost all in the prepared texts. What's chiefly added is incredulity, outrage, judgments, summations, and personal interjections.
As I noted in my immediate response to the speech, the dominant chord to my ear was listen to me -- repeated as a phrase at least four times, and as a subtext in almost every sentence; essentially, all his additions said listen to me. Below, I've classified six types of ad-lib that served this mission. In quoted passages, all italics denote Clinton's oral additions. Boldface is my emphasis.