In the United States, electoral fraud—including voter impersonation, mail-in ballot fraud, and illegal voting by noncitizens—is defined by the federal government as one of three broad categories of election crimes. Although it was significantly more prevalent in the 19th and early 20th centuries, research consistently shows it is extremely rare today, with mail-in fraud occurring slightly more often than in-person voter fraud. Comprehensive databases, such as the 2012 News21 project and the conservative Heritage Foundation's list, found fraud accounts for only a minuscule fraction of votes—for example, 2,068 alleged cases out of billions of votes cast between 2000 and 2012. Voter impersonation is particularly rare, as no election outcomes were overturned due to it between 1978 and 2018, and experts note it is illogical due to the high risk and low reward. However, false accusations of fraud have a long history, often tied to Donald Trump and the election denial movement since the 2016 and 2020 elections, making the topic a significant and contentious part of American politics.