This document summarizes a study on the impact of Twitter use on the perceived credibility of 2016 US presidential candidates. It provides background on rhetoric, persuasion, and credibility in politics. Specifically, it discusses Aristotle's modes of persuasion (pathos, logos, ethos) and how they can impact a politician's credibility. The study examined how candidates' tweets may have influenced voters' opinions according to these persuasion modes. It reviewed literature on social media and politics, finding that Twitter has become an important campaign tool. The researcher surveyed 170 subjects on their views of different candidates' credibility, finding that Bernie Sanders was viewed as one of the most credible.