The filmmaker Michael Moore has announced a large-scale effort to combat dirty tricks during the US election by stationing hundreds of people with video cameras outside polling stations.
"I'm putting those who intend to suppress the vote on notice: voter intimidation and suppression will not be tolerated," Mr Moore said in a statement.
Mr Moore, the director of the documentary Fahrenheit 9/11, said 1,200 videographers would descend on polling stations in Florida and Ohio, the two battleground states that have been the focus of some serious allegations.
The last few months have seen an unprecedented drive to register new voters there. But registrations could now be deemed invalid as a result of errors made on the forms, from corner-cutting by workers paid to sign people up, or from deliberate fraud.
In Milwaukee, in the swing state of Wisconsin, Republicans produced a list of 37,000 voters whose addresses they said were questionable, arguing they would be required to show identification at the polls or face a challenge as they cast their votes.
But Milwaukee's city attorney, who represents no party, said hundreds of addresses on the list had already been confirmed as valid, while local Democrats warned that voters could be disenfranchised simply for failing to include their apartment number as part of their street address.
Meanwhile, continuing chaos seemed inevitable in Broward County, Florida, where thousands of voters are likely to end up without a vote after their absentee ballots went missing.
Some replacement ballots were sent last week by courier, but 2,500 were only posted at the weekend by regular mail. Legally, the votes must be returned by 7 p.m. tomorrow.
Most widespread problems could result from a nationwide shortage of at least half a million poll workers, the US election assistance commission said yesterday. It pleaded with employers to give volunteers the day off so that they could help operate polling stations and count votes.
"If the criminal justice system didn't have access to jurors, the criminal justice system wouldn't exist. Poll workers are just as important as jurors," said DeForest Soaries Jr, the commission's chair.
Elsewhere, reports of suspicious campaigning activities continued to surface.
In South Carolina, the Democratic party said a letter was circulating which wrongly informed voters that they could be arrested at the polls if they had outstanding parking tickets or child-support payments.