During presidential election campaigns in the United States, it has become customary for the candidates to engage in one or more debates. The topics discussed in the debate are often the most controversial issues of the time, and arguably elections have been nearly decided by these debates. Candidate debates are not constitutionally mandated, but they are now considered an intrinsic part of the election process. The debates are targeted mainly at undecided voters; those who tend not to be partial to any political ideology or party.
Presidential debates are typically held late in the election cycle, after the political parties have nominated their candidates. The candidates typically meet in a large hall, often at a university, and usually before an audience of citizens. The formats of the debates have varied, with questions sometimes posed from one or more journalist moderators and in other cases members of the audience. The debate formats established during the 1988 through 2000 campaigns were governed in detail by secret memoranda of understanding (MOU) between the two major candidates; the MOU for the 2004 debates was, unlike the earlier agreements, jointly released to the public by the participants.