Republican presidential candidate Mitt Romney on Wednesday played the ultimate fear card and promised that someone would definitely use nuclear weapons if President Barack Obama is re-elected.

During a CNN-sponsored debate in Mesa, Arizona, the candidate explained that reducing the price of gas was less important than preventing Iran from obtaining nuclear weapons.

"The price of gasoline pales in comparison to the idea of [Iranian President Mahmoud] Ahmadinejad with nuclear weapons," Romney said. "Ahmadinejad having fissile material that he can give to Hezbollah, Hamas, and that they can bring into Latin America, and that they can potentially bring across the border into the United States to let off dirty bombs here -- or more sophisticated bombs here."

"This president has a lot of failures. I mean, economically his failures, his policies in a whole host of areas have been troubling. But nothing in my view is as serious as his failure to deal with Iran appropriately. ... This is a president who should have instead communicated to Iran that we are prepared, that we are considering military options. They are not just on the table, they are in our hand."

Romney added: "We must not allow Iran to use a nuclear weapon. If they do, the world changes and someday nuclear weaponry will be used. If I'm president, that will not happen. If we re-elect Barack Obama it will."

Possibly not since President Lyndon B. Johnson's 1964 so-called "Daisy" advertisement has a candidate so clearly suggested that a U.S. election would result in a mushroom cloud.

U.S. Defense Secretary Leon Panetta admitted in January that Iran was not yet even trying to develop nuclear weapons.

Watch this video from CNN, broadcast Feb. 22, 2012.