Political attack ads may leave voters with a bad feeling about a candidate, even if they don’t remember the accusations.

Now that the midterm elections are over, Kristina Harrison, a clinical assistant professor of marketing at Indiana University’s Kelley School of Business, says there’s a reason campaigns keep using them.

“Just keep being exposed to something over and over and over again, even if it’s something that you don’t totally agree with,” Harrison said. “You start to think, well, maybe there’s something true to this.”

Harrison says voters may not remember the specific accusations, but they remember how the ads made them feel.

She points to a concept called moral disgust, which can cause people to judge candidates more harshly.

That reaction doesn’t always help the candidate behind the ad. Some voters end up believing both candidates are bad choices.

“They work, but we also don’t like them either,” Harrison said. “It’s kind of a discrepancy between something that you might not like, the fact we might actually hate the fact, but it might be effective in changing how we vote.”

Harrison says attack ads can also reinforce opinions voters already have. But for people who haven’t made up their minds, repeated accusations could help sway their decisions at the ballot box.