Political observers have detected a noticeable uptick in American political incivility in recent years, culminating with several moderate senators recently citing the rise of hard-core partisanship as the reason for their retirement. Supporting these accusations of unprecedented incivility with empirical evidence can be difficult, as notions of what constitutes appropriate, civil behavior are subjective and can vary across the political context of different eras. Was it more uncivil, for example, for William Jennings Bryan to accuse his political opponents of crucifying other Americans on a cross of gold than it was for a member of Congress to yell “You lie!” at the president in the nation's Capitol? Assessing the incivility of these statements requires determining the effect each had on political opponents' abilities to maintain a functional relationship despite their disagreement over policy outcomes. Nevertheless, many politicians, political observers, and scholars are truly concerned that current levels of incivility are indeed worse, not only damaging the ability to resolve complex public problems, but threatening the long-term stability of America's governing institutions. Largely focusing on changes in institutional structures and elite behavior, scholars identify numerous explanations for this trend.