Story highlights Robby Mook, Clinton's campaign manager, charged the Sanders' campaign with purposely misleading voters about endorsements

Sanders' 30-second spot cites a series of outlets who have endorsed the Vermont senator, but included The Valley News and the Nashua Telegraph, two papers that have not backed him

Durham, New Hampshire (CNN) Hillary Clinton and fact check organizations faulted Bernie Sanders on Thursday for what they called a misleading ad that said two newspapers were backing the Vermont senator when, in fact, they had not.

Robby Mook, Clinton's campaign manager, charged the Sanders' campaign with purposely misleading voters about endorsements in a Medium post.

"Now, campaigns can (and will) make mistakes. But the same thing has happened over and over again," Mook said, noting how Sanders' campaign used a quote from the Des Moines Register in an ad last week, despite the paper never endorsing him. "In other words, this evidently wasn't a mistake. This was a strategy."

Sanders' 30-second spot cites a series of outlets who have endorsed the Vermont senator, but included The Valley News and the Nashua Telegraph, two papers that have not backed him.

"For the record, despite @BernieSanders deceptive ad to the contrary, @NashuaTelegraph has not endorsed any Dem prez candidate," Roger Carroll, the paper's executive editors, tweeted on Wednesday.

Read More