Rumors, misleading claims and outright lies about elections and fraud are flooding online spaces in unprecedented numbers in the run-up to the US elections.

Hundreds of incidents of alleged voting irregularities are being collected and disseminated by individuals and independent and Republican-affiliated groups. A small number of contributions also come from Democrats.

The U.S. government has also alleged that foreign actors, including Russia, are spreading fake videos to undermine trust in the electoral process.

The whirlwind of misinformation spreading online is posing a challenge for election officials, who must debunk rumors and reassure voters as they prepare to conduct Election Day on Tuesday.

Many posts alleging election irregularities support the Trump campaign's false claim that the former president won the 2020 election and suggestions that he may be cheated out of victory again on November 5.

When asked whether he would accept the 2024 election results, Donald Trump said during the presidential debate in September that he would do so if it was a “fair, legal and good election.”

A majority of Americans — 70% — expect him to reject the result if he loses, according to a CNN/SSRS poll released Monday.

Just this week, Trump himself claimed that there was widespread fraud in a key swing state.

“Pennsylvania is cheating and getting caught on a scale never seen before,” Trump posted on his Truth Social network. “REPORT FRAUD TO THE AUTHORITIES. Law enforcement must act NOW!”

The accusation came after officials in three Pennsylvania counties said they were working with local law enforcement to investigate some voter registration applications for possible fraud.

As Trump and his allies seized on the announcements, the state's top election official, Republican Al Schmidt, urged caution and warned voters to beware of “half-truths” and disinformation on social media.

“This is a sign that the built-in safeguards in our voter registration process are working,” he said.

The BBC has seen hundreds of allegations of election fraud online, on social media, on message boards and in chat groups. Some of these posts have been viewed millions of times each.

The posts implied that it was easy for non-citizens to vote, made false claims about voting machines and sowed distrust in the ballot counting process.

A video appears to show recently arrived Haitians voting in Georgia.

The BBC has found clear evidence, including false addresses and archive photos, that suggest the video is fake. US security officials announced this on Friday it was made by “Russian influencers”.

Another person on

This is also a fake and part of an action coordinated on the fringe forum 4chan. The ballot pictured comes from Florida, a state that requires ID to vote in person and is about a 20-hour drive from the Canadian border.

Meanwhile, in Northhampton County, Pennsylvania, it turned out he was a postal worker issuing mail-in ballots, but the video has been viewed more than five million times.

Experts worry that the flood of misinformation just before Election Day could undermine people's confidence in the results – or lead to threats and violence in the run-up to the election and beyond.

It's happened before.

In the hours and days after the 2020 presidential election, while votes were still being counted, then-President Trump took to social media to allege fraud and falsely claim that he was the true winner of the election. “Stop the steal” became the slogan of his support movement to overturn the results.

On social media, chat rooms, and street protests, conspiracy theorists reported widespread election fraud, culminating in an insurrection at the U.S. Capitol on January 6, 2021.

Meanwhile, in battleground states like Georgia, election officials — officials whose job it is to oversee elections — have faced death threats.

While the number of false election claims increased after the 2020 election, groups that monitor this type of activity say it began well before Election Day this year.

Wendy Via, founder of the Global Project Against Hate and Extremism (GPAHE), said some far-right and right-wing activists “are preparing for the election to be stolen in a way that was not the case in 2020.”

“We cannot emphasize enough the role of conspiracy theories in all of this,” she said.

These doubts have already reached Trump supporters on site. At a rally this week in Wisconsin, another key swing state, several people said they believed only illegal activity would prevent the Republican candidate from winning.

“I'm very confident in Trump as long as there's no fraud,” said Brad Miller of Green Bay, who mentioned he had already heard rumors of fraud. “Our only hope is that it’s not big enough to change the outcome.”

After the 2020 election, Trump's team filed dozens of lawsuits alleging voter fraud in several states, but none were successful.

Experts say isolated incidents of voter fraud and administrative errors continue to occur in U.S. presidential elections held in all 50 states and involving more than 150 million voters in 2020.

But real incidents are now being cataloged and shared online on an unprecedented scale, and used alongside fake posts as evidence of widespread fraud.

Dozens of ballots were found in a storm drain in Southern California. Despite the unknown circumstances surrounding the event, online partisans immediately suspected deliberate fraud.

“You WILL cheat,” reads one of the thousands of comments posted.

As cases have emerged in recent days — including ones in Pennsylvania and a Chinese student charged with illegal voting in Michigan — authorities have repeatedly said their investigations are examples of the robustness of election protections.

But those who believe conspiracy theories about widespread fraud see these incidents as evidence of a coordinated plan by Democrats to “rigge” the election.

“Look at this new fraudulent voter scam,” was a typical comment in response to the news from Pennsylvania. “Democrats are already doing their best to steal another election.”

The overall effect could have catastrophic effects on trust in democracy, experts say.

“These incidents are catnip for those who want to undermine confidence in the election results,” said Luis Lozada, executive director of Democracy Works, a nonprofit group that disseminates information about elections.

The bulk of election fraud claims circulating on social media have been supported by a network of allegations-collecting groups.

Groups like Texas-based True The Vote, founded in 2009, have long been at the forefront of questioning the security of elections.

On an app developed by True the Vote called VoteAlert, supporters post examples of alleged voting irregularities.

They have made a wide range of claims, from minor security breaches to allegations of deliberate election manipulation. The organization also has people monitoring live-streaming cameras trained on ballot boxes in a number of states. Many local officials have repeatedly outlined the steps they have taken to make the boxes safe.

“We hope we don’t see anything on these mailboxes,” True the Vote founder Catherine Engelbrecht said at one of her recent regular online meetings for supporters.

But she also suggested that groups close to Democrats were aiming to commit large-scale voter fraud.

“If they want to try to remove the kinds of things we saw in 2020, they will most likely get away with it because we have eyes literally everywhere,” she added.

The BBC contacted True the Vote for comment.

A number of other groups are urging supporters to report alleged irregularities.

Elon Musk's Political Action Committee for America has 50,000 members, with several posts going online every minute, almost around the clock.

Other efforts include the Election Integrity Network, a group founded by a former Trump lawyer that challenges voter registrations and recruits poll watchers — partisan observers who visit polling places.

The volume of news on these platforms – along with the vagueness of some claims and often anonymous sources – makes it nearly impossible to verify every claim.

The groups and the Trump campaign say these efforts are solely to ensure the integrity of the vote. The BBC contacted the Trump campaign for comment.

The impact of this is unpredictable.

The Department of Homeland Security said election conspiracy theories could lead to actions by domestic extremists in a memo reported by U.S. media, including BBC affiliate CBS, on Monday.

And observers expect the wave of misinformation to continue well beyond Election Day. Polls suggest the election will be one of the closest in modern U.S. history. It could take days to count all the votes and determine the winner.

Luis Lozada of Democracy Works says the elections are being conducted in an “ecosystem of mistrust.”

But despite the doubts sown, he says, “accurate information is making its way to the public.”

“Election officials are working very hard to ensure that elections are conducted properly, as they were in 2020,” Mr. Lozada said. “That won’t stop people from telling anecdotes and trying to poke holes in the matter.”

With reporting by BBC Verify