In the United States, electoral fraud, or voter fraud, involves illegal voting in or manipulation of United States elections. Types of fraud include voter impersonation or in-person voter fraud, mail-in or absentee ballot fraud, illegal voting by noncitizens, and double voting. The United States government defines voter or ballot fraud as one of three broad categories of federal election crimes, the other two being campaign finance crimes and civil rights violations.

Electoral fraud is very rare in the United States. Mail-in voter fraud occurs more often than in-person voter fraud. In the last half-century, there have been only scattered examples of electoral fraud affecting the outcomes of United States elections, mostly on the local level. Electoral fraud was significantly more prevalent in earlier United States history, particularly in the 19th and early 20th centuries, and has long been a significant topic in American politics. False accusations of electoral fraud also have a long history, and since the 2016 and 2020 elections have often been associated with Donald Trump and the election denial movement in the United States. Frequency Research has consistently found that voter fraud in the United States is very rare. Fraud is more likely to occur in and affect the outcome of local elections, where the potential impact of a small number of votes can be greater. Some experts have said voter fraud can be difficult to prove or find, depending on the circumstances, although experts generally consider widespread cheating easy to detect.

The term fraud is often used to describe all illegal voting cases even where there was no intent. Cases of illegal voting are often accidental.

Nationwide databases In 2012, News21, an Arizona State University journalism project, published a database of 2,068 alleged voter fraud cases reported between 2000 and 2012. This represented about 0.000003 cases for every vote cast. 46 percent of cases also resulted in acquittals, dropped charges or decisions not to bring charges. News21 gathered the information by sending public records requests to elections officials and prosecutors and reviewing court records and media reports and created the most comprehensive database to date of electoral fraud despite not being able to obtain data from all jurisdictions. The database also includes instances of voter intimidation.

The Heritage Foundation, a conservative think tank, publishes an incomplete database of voter fraud cases brought by prosecutors since 1979. As of November 2023, there were 1,465 proven cases of voter fraud listed in 44 years, an average of 33 cases per year. This represents a tiny fraction of total votes. In Texas, for example, Heritage found 103 cases of confirmed voter fraud between 2005 and 2022, in a period where 107 million ballots were cast, or 0.000096% of all ballots cast. Heritage has stated that the database is only a "sampling" and not comprehensive.

Voter impersonation

Voter impersonation, or in-person voter fraud, occurs when someone votes in-person under the identity of someone else. It is extremely rare. Between 1978 and 2018, no elections were overturned by courts due to voter impersonation fraud. Cases of voter impersonation are often difficult to prove. Rutgers professor Lorraine Minnite has maintained that voter impersonation is illogical from the perspective of the perpetrator due to the high risk and limited upside of casting one vote. If caught, perpetrators of voter impersonation can face up to 5 years in prison and a fine of up to $10,000 for citizens and deportation for immigrants. Proponents of voter identification laws have argued that it can be difficult to detect voter impersonation if voter ID is not required. University of Virginia law professor Michael D. Gilbert agreed with Minnite in 2014 that theory and evidence suggest voter impersonation "rarely occurs", though agreed with voter ID proponents that "the failure to observe fraud does not mean that no fraud takes place". Gilbert noted that it is difficult for someone to coordinate widespread voter impersonation to steal an election, as even if they paid people to vote in-person for their preferred candidate, the secret ballot ensures they could not confirm whether these people voted the way they were paid to.

ABC News reported in 2012 that only four cases of voter impersonation had led to convictions in Texas over the previous decade. News21 identified a total of 10 cases of alleged voter impersonation in the United States between 2000 and 2012. Another 2012 study found no evidence that voter impersonation (in the form of people voting under the auspices of a dead voter) occurred in the 2006 Georgia general elections. In a 2013 study, the New York City Department of Investigation (DOI) sent investigators to vote under the names of 63 ineligible voters, who were either deceased, felons or had moved outside New York City. 61 of those investigators were allowed to illegally vote under their assumed identities. One of the two who was not allowed to vote was recognized by the mother of the felon they were impersonating, who worked at the polling place. In five instances, investigators in their 20s or 30s successfully posed as voters age 82 to 94. The DOI report stated that this result, while not large enough to be statistically significant, "indicates vulnerability in the system".

In April 2014, Federal District Court Judge Lynn Adelman ruled in Frank v. Walker that Wisconsin's voter ID law was unconstitutional because "virtually no voter impersonation occurs in Wisconsin". A 2014 Election Law Journal study of the 2012 election found no evidence of widespread voter impersonation. In August 2014, Loyola Law School professor Justin Levitt reported in The Washington Post 's Wonkblog that he had identified only 31 credible cases of voter impersonation since 2000. The most serious incident identified involved as many as 24 people trying to vote under assumed names in Brooklyn, which would still not have made a significant difference in most American elections. News21 reviewed cases of possible voter impersonation between 2012 and 2016 in five states where politicians had expressed concerns about it, and out of 38 successful state prosecutions for voter fraud, none were for voter impersonation.

Mail-in ballot fraud

Multiple forms of voter fraud have been documented using mail-in or absentee ballots, which include the requesting and submitting of absentee ballots on behalf of other voters; ballot stuffing in absentee drop boxes; coercion of voters, since the ballot is not always cast in secret; ballots being stolen from the mail and submitted; and collection of ballots by dishonest collectors who mark votes or fail to deliver ballots. Ballot harvesting, or third parties collecting and delivering absentee ballots for voters, is also illegal or restricted in some states. While quite rare, experts say fraud occurs more often with mailed-in votes than with in-person voting. Between 1978 and 2018, at least fourteen elections were invalidated or overturned by courts due to absentee ballot fraud, twelve of which were at the local level (for such offices as county clerk, sheriff, judge, and mayor).

Postal ballots have been the source of "most significant vote-counting disputes in recent decades" according to Edward Foley, director of the Election Law program at Ohio State University. In 2012, The New York Times wrote that according to election administrators, fraud in voting by mail was "far less common than innocent errors" but "vastly more prevalent" than in-person voting fraud. University of Chicago political scientist Anthony Fowler said in 2020 that fraudulently voting on behalf of someone else, tampering with ballots, coercion or vote buying could all be easier with mail-in ballots, but that in practice "the risk of widespread fraud is probably very minimal, even with all-mail elections". Loyola Marymount professor Justin Levitt stated in 2020 that misconduct in mail voting is "meaningfully more prevalent" than with voting in person, but that misconduct "still amounts to only a tiny fraction" of mail ballots. Lonna Atkeson, an expert in election administration, said about mail-in voting fraud, "It's really hard to find... The fact is, we really don't know how much fraud there is... There aren't millions of fraudulent votes, but there are some." Lorraine Minnite said "my sense is that it is not much more frequent than in-person voter fraud, which rarely occurs." Richard Hasen, a professor at University of California, Irvine School of Law, said that "problems are extremely rare in the five states that rely primarily on vote-by-mail."

An analysis by News21 found 491 known cases of absentee ballot fraud between 2000 and 2012. In April 2020, a voter fraud study covering 20 years by the Massachusetts Institute of Technology found the level of mail-in ballot fraud "exceedingly rare" since it occurs only in "0.00006 percent" of individual votes nationally, and, in one state, "0.000004 percent – about five times less likely than getting hit by lightning in the United States." A 2020 Washington Post analysis of data from three vote-by-mail states (Colorado, Oregon and Washington), with help from the Electronic Registration Information Center (ERIC), found that out of about 14.6 million mail votes cast in 2016 and 2018 officials had flagged just 372 possible cases of double voting or voting on behalf of deceased people. In many cases, ballot drop boxes are placed in locations where they can be monitored by security cameras or election staff.

Noncitizen voting

Illegal voting by noncitizens occurs when noncitizens vote in elections they are not eligible to, such as federal elections. It is extremely rare. This is due in part to the more severe penalties associated with the practice including deportation, up to five years of incarceration or fines, as well as the jeopardizing of naturalization efforts. The federal form to register a voter requires a unique identification number such as a Social Security or driver's license number. New voters must check a box attesting that they are a citizen, and are not required to provide documentary proof of citizenship when registering. States typically have safeguards to prevent noncitizen voting, although the extent to which states verify citizenship of voters differs. When noncitizens are added to voter rolls, it is usually by mistake, as the result of a federal law that requires states to offer people voter registration when they visit a motor vehicle office. Sometimes it also appears that more noncitizens are on voter rolls than there are because they became naturalized citizens but have not yet been back to the DMV to update their citizenship status in the DMV database.