The difference is clear!

It was one thing to drop the bombs in 1945, when nobody really knew what they would do, but today, now that their effects are known, there is no excuse for anyone wanting to own such weapons. That's why the very clear difference between Obama and McCain about this issue is very important.

OBAMA:

Toward a Nuclear Free World: Obama will set a goal of a world without nuclear weapons, and pursue it. Obama will always maintain a strong deterrent as long as nuclear weapons exist. But he will take several steps down the long road toward eliminating nuclear weapons. He will stop the development of new nuclear weapons; work with Russia to take U.S. and Russian ballistic missiles off hair trigger alert; seek dramatic reductions in U.S. and Russian stockpiles of nuclear weapons and material; and set a goal to expand the U.S.-Russian ban on intermediate- range missiles so that the agreement is global.

MCCAIN:

John McCain strongly supports the development and deployment of theater and national missile defenses. Effective missile defenses are critical to protect America from rogue regimes like North Korea that possess the capability to target America with intercontinental ballistic missiles, from outlaw states like Iran that threaten American forces and American allies with ballistic missiles, and to hedge against potential threats from possible strategic competitors like Russia and China. Effective missile defenses are also necessary to allow American military forces to operate overseas without being deterred by the threat of missile attack from a regional adversary.

N.B. North Korea certainly does NOT "possess the capability to target America with intercontinental ballistic missiles" but they rather possess the ability to hit Japan and South Korea, as well as Vladivostok and parts of China.

And there are reports (I'm having trouble googling them just now) that the US military no longer wants nuclear weapons. They are too dangerous and serve no purpose. Nobody wants nuclear weapons detail, after that little incident of the lost nukes especially.