Donald Trump isn’t letting up on his claims that a rigged system threatens his victory on Election Day, although repeated investigations have found no evidence of widespread fraud at the polls.
As he and Hillary Clinton prepare for their last debate of the presidential race, he continues to tweet about fraud at polling places and about "a dishonest and distorted media pushing Crooked Hillary." At a rally on Tuesday in Colorado, he again urged his supporters to watch the polls closely.
"They even want to try and rig the election at the polling booths, where so many cities are corrupt, and voter fraud is all too common," Trump said. "And then they say, oh there's no voter fraud in our country, there's no voter fraud, no, no, there's no voter fraud. Take a look at St. Louis, take a look at Philadelphia, take a look at Chicago."
The Brennan Center for Justice at the New York University School of Law — the publisher of Justin Levitt’s widely quoted study, "The Truth About Voter Fraud" — calls fraud at the polls "vanishingly rare," so unusual that it does not come close to what would be needed to rig an election.
Levitt wrote in The Washington Post two years ago that he had found 31 allegations since 2000 of someone pretending to be someone else at the polls. More than 1 billion ballots were cast in that period in general and primary elections.
The Carnegie-Knight News21 program -- made up of journalism students and graduates -- analyzed 2,068 alleged cases in 50 states in the decade before 2012 and could document only 10 instances of in-person voter impersonation. There were 491 cases of absentee ballot fraud and 400 cases of registration fraud —out of 146 million registered voters.
Another investigator, Lorraine Minnite, the author of the book "The Myth of Voter Fraud" and a professor of political science at Rutgers University in Camden, New Jersey, says the claim that voter fraud threatens American elections is "itself a fraud."
"It’s a rare occurrence," said Minnite, who has been studying voter fraud for 15 years. "I'm talking specifically about the kind of fraud that voters might commit, which really is mostly limited to misrepresenting their identity or misrepresenting their eligibility."
President Barack Obama on Tuesday called Trump's attempt to discredit the election irresponsible. No serious person would suggest it was possible to rig U.S. presidential elections because they involve too many votes and are so decentralized, he said.
"So I'd invite Mr. Trump to stop whining and go make his case to get votes," Obama said.
Although Trump's running mate, Mike Pence, said on Tuesday that voter fraud was real in pockets of the country, other Republicans are refuting claims of a rigged election. U.S. Sen. Marco Rubio, a former Trump rival, said that there was no evidence for Trump's statements.
"We have 67 counties in this state, each of which conduct their own elections," he said. "I promise you there is not a 67-county conspiracy to rig this election."
Another Trump rival for the GOP nomination, Ohio Gov. John Kasich, strongly disagreed with Trump's claims.
"To say that elections are rigged and all these votes are stolen, that's like saying we never landed on the moon, frankly, that's how silly it is," Kasich told CBS Wednesday. "No, I just, I don't think that's good for our country, for our democracy, and I don't believe that we have any massive fraud."
Even Trump surrogate New Jersey Gov. Chris Christie pushed back, telling NBC News, "I'm convinced that the election will be a fair one and that the process will be one that will accepted by the American people."
Here's a closer look at some allegations of voter fraud:
Dead Man Voting
Former New York City Mayor Rudy Giuliani, another Trump surrogate, said on CNN over the weekend that, "Dead people generally vote for Democrats rather than Republicans."
In New York in 2002 and 2004, 2,600 dead voters were alleged to have cast ballots, based on a match of voter rolls to death records. No cases of fraud were substantiated, the Brennan Center says. Seven were found to be a result of a database mismatch or an accounting error. Even if all of the 2,593 remaining cases involved fraud, the rate would be 0.02 percent, the Brennan Center said.
In New Jersey, Republican officials compared voter registration lists, Social Security death records and other public information to allege that 4,755 dead people had voted. "No follow-up investigation appears to document any substantiated cases, and no allegedly deceased voter voted in 2005," the Brennan Center says.
And in Michigan, allegations of votes cast by 132 dead people in Detroit were challenged by the state's Republican secretary of state in 2006. The office said that 132 absentee ballots were mailed to voters who died in the weeks before Election Day, Minnite wrote in a 2007 study, "The Politics of Voter Fraud." Ninety-seven were never returned, 27 were returned before the voters' deaths — a correction ignored by activists, Minnite said.
Allegations of double voting in New York can be found from elections in 1996, 1998, 2000, 2002 and possibly others, according to the Brennan Center. In 2004, between 400 and 1,000 voters were alleged to have voted both in New York and Florida, according to matches between New York and Florida voting rolls. The Brennan Center said it as aware of only two cases being substantiated.
However, a 2013 New York City investigation of the city's Board of Election found systemic problems with accountability, transparency and dysfunction, including defects in the voters rolls, improper instructions that voters should "vote down the line" and a persistent failure to address ballot design issues.
In New Jersey, 4,397 people were alleged to have voted twice and 6,572 who were registered in New Jersey and five other states: New York, Florida, Pennsylvania, North Carolina and South Carolina. The Brennan Center found that only eight cases were actually documented through signatures on poll books with at least five signatures appeared to match. If all eight cases were proved, the double voting rate would be 0.0002 percent, according to the Brennan Center.
Other cases were alleged in New Hampshire in 2004 — of voters listed multiple times on city rolls or of people voting from improper addresses. The Brennan Center says that of the 676,227 ballots cast in 2004 general election in New Hampshire, two invalid cases were substantiated and two others were still under investigation. Even of all four were substantiated, the rate would be 0.0006 percent.
Voting by Non-citizens
The Brennan Center says it found no documented cases in which non citizens intentionally registered to vote or voted knowing they were ineligible. In Washington state in 2004, documentation appears to show that two votes were cast by non citizens in King County, the center says. The rate: 0.0002 percent.
Another example: In Hawaii in 2000, 553 apparent non citizens were alleged to have registered. Of those 144 documented that they had become citizens and at least 61 asked to cancel their registration. Others were stopped at the polls.
The students participating in the Carnegie-Knight News21 program found 56 cases of non-citizens voting.
The Carnegie-Knight News21 program, as part of an investigation into the need for photo IDs, found 10 cases of voter impersonations -- in Alabama, California, Colorado, Kansas, New Hampshire and Texas. There were 146 million registered voters in the United States at the time.
"All were isolated and showed no coordinated efforts to change election results," the students wrote in 2012.
Dogs at the polls
The Brennan Center found two cases of ballots submitted in the name of a dog -- one from "Duncan MacDonald" in 2006 and 2007, although it notes that the ballot was labeled VOID and signed with a paw print; and one from "Raku Bowman" in 2003. The second was counted by volunteers in local elections in Venice, California.