Psychologists have noted that analogical reasoning is pervasive in argumentation (Kuhn, 1992; Holyoak, 1997), but the forms these arguments can take varies substantially. Memes are one common format or argument-by-analogy. Memes are widely recognized images or templates that compares two situations to each other for the purpose of making some (often questionable) point. Even though memes-as-arguments are readily visible on social media, the persuasiveness of this category of argument-by-analogy---and specifically the features that predict their persuasiveness---have not been established. This study investigates whether and in what ways arguments by analogy, delivered in the form of a meme, are persuasive. We develop a large set of memes representing common meme structures, political leaning, and familiarity and examined how these factors predict a meme's perceived clarity, persuasiveness, and memorability, along with these memes effects on beliefs about issues such as climate change, immigration, and racism.