ATLANTA -- Donald Trump has warned for weeks of a "rigged" election, telling his supports to watch out for large-scale voter fraud -- despite a lack of evidence that it exists. In the past few days, Trump has specifically raised concerns about people fraudulently voting using the names of dead people and cited research showing 1.8 million deceased people are still listed on state voter rolls.

Here's a look at Trump's latest claim and what the facts show:

TRUMP:

During a campaign rally Saturday in Gettysburg, Pennsylvania, Trump brought up his concerns about voter fraud, saying "the system is totally rigged and broken."

He added: "According to Pew, there are 24 million voter registrations in the United States that are either invalid or significantly inaccurate, and when I say that, there are such inaccuracies it's unbelievable. 1.8 million dead people are registered to vote. And some of them are voting. I wonder how that happens. 2.8 million people are registered in more than one state. These are numbers, folks, these are numbers."

THE FACTS:

The Pew Center on the States issued a report in 2012 saying the nation's voter registration system was "plagued with errors and inefficiencies that waste taxpayer dollars, undermine voter confidence, and fuel partisan disputes over the integrity of our elections." The report urged states to expand online voter registration and other online tools to allow voters to update their information, saying paper-based systems presented several opportunities for errors.

Trump correctly cited Pew's findings in that report, which found that approximately 24 million, or one of every eight, voter registrations were no longer valid or significantly inaccurate and that more than 1.8 million deceased individuals were listed as voters. He also was correct in noting that approximately 2.7 million people have registrations in more than one state.

However, a majority of states have taken action in recent years to address concerns raised in the Pew report. In addition, the Pew report does not say that any of the inaccuracies led to a system that is vulnerable to widespread voter fraud.

In an update posted last week on its website, the Pew Center said election officials have worked to upgrade their voter registration systems.

It noted that 40 states now provide or have passed legislation allowing for online voter registration and 20 states have signed up for the Electronic Registration Information Center. That system is administered by the states and alerts election officials to cases in which a voter's information may be out of date.

The system has contacted more than 4.5 million people who had moved, but not updated their voter registration information, according to Pew.

Ohio is among the states that participate in the program. Ohio Secretary of State Jon Husted, a Republican, has said voter fraud is rare and has pushed back against Trump's claims the election could be compromised. An estimated 515,000 deceased voters have been removed from Ohio's registration records since Husted took office in 2011.

There have been isolated cases in which ballots have been cast in the name of a deceased individual, including two instances in 2012 in Husted's Ohio.

In one case, a 54-year-old nun pleaded guilty to a charge of illegal voting after acknowledging she filled out an absentee ballot on behalf of a fellow nun who had recently died. The other involved allegations that a 75-year-old man had cast an absentee ballot on behalf of his recently deceased wife.

"We've been working hard to keep Ohio's voter rolls as up-to-date and accurate as possible so that only eligible voters are registered and casting ballots," said Joshua Eck, Husted's spokesman. "As Secretary Husted commonly says, voter fraud happens -- it's rare -- and when we catch it, we hold people accountable."

Experts say cases of voter fraud involving dead people are isolated. They also say it would be an inefficient way to rig a presidential election, given that the fraud would have to be conducted one voter at a time and would be effective only in places where the race is close enough that the outcome could be swayed.

There are more than 9,000 election jurisdictions nationwide and hundreds of thousands of polling places.

"Although entertaining, every time there are claims of hordes of dead people voting, those claims are debunked upon closer scrutiny," said Wendy Weiser, head of the democracy program at the Brennan Center for Justice at NYU's School of Law. "There has been no incident in recent memory in which people were able to impact an election by mobilizing fraudsters to impersonate dead people at the polls."

Weiser said a more pressing concern is that living people are sometimes mistakenly identified as dead and removed from a state's voter registration database, posing a challenge to them voting legally on Election Day.