Kaleb Vanfosson stunned a rally meant to drum up support for Mrs Clinton when he suddenly slammed the Democrat nominee and told the crowd not to vote for her.
But, much to his surprise, Mr Vanfosson was cheered by the crowd – before Mrs Clinton’s campaign crew intervened and dragged him off stage.
Mr Vanfosson, a political activist at the local university, was booked to warm up the crowd with a pro-Clinton speech in the swing state of Iowa.
According to the Clinton campaign, he was scheduled to give a speech about Democrats uniting around the candidate., but instead gave a speech about “how terrible Hillary is.”
However, he appeared to dump his script halfway through and launch into a diatribe against Mrs Clinton.