KNOXVILLE, Tenn. (WVLT) -- GOP congressional candidate Scott DesJarlais has backed out of a planned debate against Democratic incumbent Lincoln Davis.

The showdown was to happen tonight in McMinnville but DesJarlais' camp says it would've been another chance for Davis to "spew more venom and deception." Davis' camp says desjarlais is, "afraid."

It's been a brutal campaign season littered with one political attack ad after the other. But candidates running negatives ads could get an unintended result.

"If I see a really negative ad and it's endorsed by the other candidate, I might think twice about voting for them," said Valerie Bettis.

Political science expert, Dr. William Boone, who's no relation, says negative ads could galvanize the opponent's base. "It may work to generate some enthusiasm among folks who were not coming out at first," he said.

Dr. Ron Brown is a noted psychologist who says negative ads play on voters' fears and emotions to drive them to the polls. He also says negative ads could drive voters away from the polls. "It can affect the vote in some way. People throw up their hands and say I'm not voting for either one of these two clowns because they're both saying things I don't care to hear."

Dr. Boone says like them or not, negative ads usually have some influence on voters. "Many of them look at negative ads, remember the ads, and sometimes act upon the information in the ads," he said.