The Conversation | President Donald Trump and former Vice President Joe Biden took part in a presidential debate Sept. 29 that exemplified the lack of civility in American politics. The president frequently interrupted and spoke over his challenger, Biden told Trump to “shut up,” and few issues were discussed in enough depth to provide much information to undecided voters. We asked three scholars to discuss themes brought up by moderator Chris Wallace of Fox News, who struggled throughout the debate to keep control.