Posed that scenario while campaigning Friday in this early primary state, Romney said he didn't want to say much more.
"The answer is you would retaliate and you'd retaliate in a very dramatic and clear way. I don't want to be terribly more specific than that," the former Massachusetts governor said.
"But there's no question that people understand that the reason that we have the thousands upon thousands of nuclear warheads we have is that we intend to protect ourselves. And I would never shrink from protecting the American nation, the American people, nor shrink from retaliation if somebody used something as awful as a nuclear device. We will be safe."
The key is preventing nuclear proliferation, Romney said. He cited Iran, which has been accused of seeking to develop nuclear weapons, a charge its leaders have denied while claiming it's interested only in a nuclear energy program.
"It's time for us to dramatically tighten the sanctions on Iran and to get our friends around the world to do the same," Romney said. People in Iran need to know that "going down the nuclear path is a source of peril, not a source of pride," he said.
This sounds like a president of the United States, not the craven liberal musings of Obama and his "I think it would be a profound mistake for us to use nuclear weapons in any circumstance."