He was asked this question yesterday by the WaPo editorial board. Here was his (first) answer:
I don’t want to use, I don’t want to start the process of nuclear. Remember the one thing that everybody has said, I’m a counterpuncher. Rubio hit me. Bush hit me. When I said low energy, he’s a low-energy individual, he hit me first. I spent, by the way he spent 18 million dollars’ worth of negative ads on me. That’s putting [MUFFLED]....
I’ll tell you one thing, this is a very good looking group of people here. Could I just go around so I know who the hell I’m talking to?
Vintage Trump: (1) duck the question by (2) making it all about him and seguing into attacking primary opponents who've already dropped out, followed by (3) a smarmy faux compliment to his audience. He wasn't asked what he would want to do - who in their right mind would want to use nuclear weapons? - he was asked if he would use tactical nuclear weapons against ISIS.
A candidate who had done his issues homework and knew what he was talking about would have replied, first, by pointing out that the U.S. possesses little in the way of a tactical nuclear capability anymore - Pershing II MRBMs, gone, nuclear 155mm artillery shells, gone, nuclear-tipped Tomahawk cruise missiles, gone. All there is is a handful here and in Europe under NATO auspices:
Nevertheless, according to unclassified reports, the United States did reduce the number of nuclear weapons deployed in Europe and the number of facilities that house those weapons during the George W. Bush Administration. Some reports indicate that the weapons were withdrawn from Greece and Ramstein Air Base in Germany between 2001 and 2005. In addition, reports indicate that the United States withdrew its nuclear weapons from the RAF Lakenheath air base in the United Kingdom in 2006. According to unclassified reports, the United States now deploys 160-200 bombs at six bases in Belgium, Germany, Italy, the Netherlands, and Turkey. Some of these weapons are stored at U.S. bases and would be delivered by U.S. aircraft. Others are stored at bases operated by the “host nation” and would be delivered by that nation’s aircraft if NATO decided to employ nuclear weapons.
Second, a candidate who had done his issues homework and knew what he was talking about would have pointed out that U.S. policy for over half a century has been that (1) we do not use nukes first and (2) we neither use nor threaten to use them against non-nuclear countries. Which means that the Islamic State would need to (1) nuke us and (2) would have to be proven to have been behind the attack before we could retaliate in kind. But that brings up the second problem of ISIS not being a recognized nation-state, in which case that retaliation in kind would constitute nuking Syria and Iraq (at the very least), neither of with which the U.S. is at war and neither of which is a member of the "nuclear club".
Third, a candidate who had done his issues homework and knew what he was talking about would have pointed out that such a retaliation in kind would, in both blast and radioactive fallout affects, cause massive collateral damage against innocents, likely much more than ISIS itself would suffer, since they intermix themselves with their captive subject population.
Fourth, a candidate who had done his issues homework and knew what he was talking about would have pointed out that the risks of igniting a larger nuclear war with Iran and especially Russia (both of whose ally would have had its territory and citizens nuked) from such a retaliation in kind would grow enormously
Fifth, a candidate who had the PR acumen God gave a doorknob would have recognized this question as a "gotcha" and segued to how ISIS can be crushed by conventional means, with sufficient "boots on the ground" to get the job done and keep it done by not running away again and abandoning our victory like Barack Obama did. But Trump's Code Pink instincts won't permit him to say that, as won't his magic wand compulsion to promise easy, simple, cost-free solutions to difficult, complicated, costly problems. Mix in his "tough guy/populist" reflex and you get, "I won't rule it out".
That's what he said this morning:
Believe it or not, the vintage Trump answer he gave to the WaPo editorial board was the better one, because nothing in it can wind up in a bazillion Hillary Clinton attack ads this fall. Which was the purpose of the "Would you nuke ISIS?" question, as any professional politician would have instantly recognized and easily avoided.
Besides, ISIS themselves know the answer to the question, even if Trump does not:
The problem obviously is that even a President Trump would be heavily constrained in any decision to use nukes, ISIS knows that, and [that] nukes would not serve our best interest. To mildly paraphrase Talleyrand, “It is worse than a crime, it is a blunder.”
Or what Trumplicans call "fighting".