Presidential debates offer the chance for the public to hear the candidates’ stance on issues ranging from foreign policy to healthcare. But aside from a presidential candidate’s track record and opinion on issues, what else affects a presidential hopeful’s likability amongst voters? Is it his or her wardrobe? Hair? Smile? Voice? It’s a question Delta Dental Plans Association sought to answer in a new survey of American voters.

“To us, the power of a smile is a big thing,” DDPA Corporate Communications Director David Irwin told Associations Now about the survey. “We wanted to gauge the public on this one.”

Turns out a candidate’s smile is not the most important quality when determining a candidate’s likability. Instead, the survey of 1,000 people, conducted by Kelton Global in late October, found that about 36 percent of polled voters agreed a candidate’s voice makes him or her more likable. How a candidate sounded was most important to voters in the Midwest, with 43 percent agreeing a candidate’s voice affected their likability, compared to 32 percent of voters in the South.

“Voice is the clear frontrunner,” Irwin said. “Voice is really what makes them more likable. That to me is surprising.”

Smile came in second place with 17 percent of voting-age Americans agreeing the power of a smile was important in determining a candidate’s likability. Irwin said he was glad to see the importance of smile was prominent and also noted that smiles mattered more to women than to men. “When we get down into the region, it matters most in the West (23 percent), almost by a landslide,” Irwin said. “When you start drilling down a little bit more, it matters to parents more than non-parents by a solid 8 percent.”

While smile ranked high, DDPA was still surprised by some of the survey results. “One thing that jumped out at me was hair,” Irwin said. Results show that it didn’t rank high in importance for most voters, with the exception of millennials. Another area that doesn’t factor much into a candidate’s likability: wardrobe.

However, It wasn’t DDPA’s intent to affect voters’ views of the candidates. “It’s interesting knowing now what so many voters pay attention to,” Irwin said, adding the results have prompted more questions. “What is it about the voice? What is it about the smile?”

Donald Trump and Jeb Bush, shown on CNN during Tuesday's Republican presidential debate. (David Becker/Reuters)