From a March 30 interview. Full transcript via MSNBC: http://info.msnbc.com/_news/2016/03/3...
MATTHEWS: Your most controversial suggestion was don't take nuclear weapons -- I mean, you may have been hooked into this by (inaudible).
TRUMP: Don't take what?
MATTHEWS: Nuclear weapons off the table.
I have been trying to think of how we could conceivably use a nuclear weapon in the Middle East or in Europe in fighting ISIS. Where can you -- and why put it on the table or leave it on the table if you can't imagine where to use it?
TRUMP: Well, I didn't say, "Don't take it." I said I would be very, very slow and hesitant to pull that trigger.
MATTHEWS: Well, why would you -- why wouldn't you just say, "I don't want to talk about it. I don't want to talk about nuclear weapons. Presidents don't talk about use of nuclear weapons"?
TRUMP: The question was asked -- we were talking about NATO -- which, by the way, I say is obsolete and we pay a dispropor...
MATTHEWS: But you got hooked into something you shouldn't've talked about.
TRUMP: I don't think I -- well, someday, maybe.
MATTHEWS: When? Maybe?
TRUMP: Of course. If somebody...
MATTHEWS: Where would we drop -- where would we drop a nuclear weapon in the Middle East?
TRUMP: Let me explain. Let me explain.
Somebody hits us within ISIS, you wouldn't fight back with a nuke?
MATTHEWS: No. To drop a nuclear weapon on a community of people that are...
TRUMP: No, no, but you can't say -- first of all, you don't want to say, "Take everything off the table..."
MATTHEWS: No, just nuclear.
TRUMP: ... because you'd be a bad negotiator if you do that.
MATTHEWS: Just nuclear.
TRUMP: Look, nuclear should be off the table. But would there be a time when it could be used, possibly, possibly?
MATTHEWS: OK. The trouble is, when you said that, the whole world heard it. David Cameron in Britain heard it. The Japanese, where we bombed them in '45, heard it. They're hearing a guy running for president of the United States talking of maybe using nuclear weapons. Nobody wants to hear that about an American president.
TRUMP: Then why are we making them? Why do we make them? We had (inaudible).
MATTHEWS: Because of the old mutual assured destruction, which Reagan hated and tried to get rid of.
TRUMP: (inaudible) I was against Iraq. I'd be the last one to use the nuclear weapon.
MATTHEWS: So can you take it off the table now?
TRUMP: Because that's sort of like the end of the ball game.
MATTHEWS: Can you tell the Middle East we're not using a nuclear weapon on anybody?
TRUMP: I would never say that. I would never take any of my cards off the table.
MATTHEWS: How about Europe? We won't use it in Europe?
TRUMP: I -- I'm not going to take it off the table.
MATTHEWS: You might use it in Europe?
TRUMP: No, I don't think so. But I'm not taking...
MATTHEWS: Well, just say it. "I will never use a nuclear weapon in Europe."
TRUMP: I am not -- I am not taking cards off the table.
TRUMP: I'm not going to use nuclear, but I'm not taking any cards off the table.
The trouble is, the sane people hear you and the insane people are not affected by your threats. That's the trouble. The real fanatics say, "Good. Keep it up."
TRUMP: I think -- I think they're more affected than you might think.