"Where is the river?" the reporter asked.
Ms McEnany, rather than answering the question, launched into a defensive tirade accusing the reporter of "missing the forest for the trees" and accusing him and others of lacking "journalistic curiosity."
"The other day [Mr Trump] said 'they found a lot of ballots in a river.' Who is they?" the reporter asked. "Who is 'they,' that found those ballots, and where is this river, anywhere in this country?"
McEnany claimed the "local authorities" were the ones who found the ballots in a ditch in Wisconsin. The reporter asked if that meant that Mr Trump misspoke, which McEnany denied. Then the reporter read Mr Trump's quote back to her, in which he claimed ballots were dumped in rivers and creeks.
At that point, Ms McEnany accused him of being shortsighted.
"I cover the news, I like to report accurately in the news, and the president says 'they found a lot of ballots in a river', I just want to know where the river is," the reporter shot back.
Ms McEnany then accused him ignoring the larger issue, which was alleged reports of ballots for Mr Trump going missing or being left uncounted.
She then claimed the press lacked "journalistic curiosity," despite the fact that the reporter was asking her for further details.
Apart from simply fact checking the president, asking for further details - particularly for a location - for such a brazen event as people dumping ballots in a river, would provide the press with an avenue for further reporting and verification.
Mr Trump has also claimed that ballots are being sold in West Virginia.
The president's frequent claims that mail-in-voting is especially susceptible to voter fraud is not backed by any data or research.
Lawrence Norden, the director of the Election Reform Program for the Brennan Center for Justice at the New York School of Law, told USA Today that Mr Trump's constant attacks on mail-in voting are not only inaccurate, they are harmful to the electoral process.
"What he said was full of misstatements and inaccuracies," Mr Norden said. "Mail-in ballots are safe and secure. We've been voting in some form by mail since the Civil War. It's dangerous to be making these false statements and accusations so close to the election."
Mr Trump has already threatened to involve the US Supreme Court in the electoral process by casting doubt on the validity of the collected ballots.
The actual situation regarding a ditch in Wisconsin occurred on 22 September, when three trays of mail, which included some absentee ballots, were found in a ditch in Outagamie County, Wisconsin. The US Postal Service and the US Postal Inspection Service put out a statement following the discovery that it would be investigating the matter.