"How, with no seniority and a promise simply not to get along with anyone, will you accomplish any of the things you want to accomplish?" 77 year-old John Davis, a retired teacher and Democrat, shouted at McDaniel, according to The Wall Street Journal.
"What have they accomplished lately by putting us in debt?" McDaniel, who is running to secure the Republican nomination for U.S. Senate in Mississippi, shot back.
At one point Davis was wagging his finger for emphasis.
"What have they accomplished? They have accomplished airports. They have accomplished roads. They have accomplished schools," Davis said.
"Get your finger out of my face," McDaniel snapped in response. The state senator also said that the federal spending Davis was talking about was brought on "by adding trillions on my children's back, trillions of dollars we can't recover from. Our country borrows 46 cents on every dollar."
"I don't want this rote answer," Davis said. "I want to know how you will accomplish it."
Eventually McDaniel sat down and Davis was eventually "sent away" from the event, according to the Journal.
Later, during the coffee event, McDaniel said Davis should have tried to approach him in a calmer manner.
"Dissent is a good thing in this country but you don't do it in that manner," McDaniel said.
The runoff between McDaniel and Sen. Thad Cochran (R-MS) is June 24.
The Cochran campaign quickly blasted out an email to supporters on the shouting match with the subject line "Clean up on aisle 4."
"Do we really want a U.S. Senator who can’t get through the primary campaign without having four key supporters arrested for felonies; who can’t get through the primary election night without three campaign supporters and staffers breaking into a county courthouse and getting locked inside with ballots in the middle of the night; and who can’t get through a grocery store without a shouting match and nearly starting a fight with a voter?" Cochran Communications Director Jordan Russell said in a separate statement to TPM.
This post was updated.