Three years after Sept. 11, there is no consensus on whether we are safer. But presidents and would-be presidents, along with a raft of experts, agree on one thing.
The greatest danger is that Islamic terrorists will steal or acquire a nuclear warhead or the highly enriched uranium to construct a crude device. They would smuggle the weapon into a city and explode it, potentially killing hundreds of thousands of people.
Given that threat, I posed a question to a wide range of experts on nuclear terrorism, some of whom have served in senior government posts.
Imagine, I said, that terrorists set off a nuclear weapon in some Western city. The president immediately convenes a National Security Council meeting and asks, before any hard data are in, what are the most likely sources for the weapon.
Two suspects topped all lists -- Russia and Pakistan. Others making most lists included North Korea and former Soviet republics such as Belarus, Kazakhstan and Ukraine.
Russia's vast arsenal of nuclear weapons and its scattered stores of bomb-quality uranium and plutonium are vulnerable to theft and terrorist assault.
Two years ago I investigated Russia's arsenal of thousands of tactical nuclear weapons. These are smaller bombs to blow up bridges or fit in artillery shells, many of them portable enough to fit in the trunk of a compact car.
I was able to literally walk through a hole in the wall of the command headquarters of the unit that guards all of Russia's nuclear weapons. Unchallenged, I wandered a base where security equipment, including armored trains to transport warheads, is stored and repaired. I did not come away with a good feeling about the state of Russian security.
Pakistan represents a different challenge. Abdul Qadeer Khan, the man who built Pakistan's bomb, turned out to be the leading global nuclear black marketeer, selling warhead designs and equipment to Libya, Iran, North Korea and who knows who else.
"Pakistan is a shaky state in which a substantial number of people in the army and intelligence services have serious ideological ties to al-Qaida," says Harvard's Graham Allison, author of the chilling new book "Nuclear Terrorism: The Ultimate Preventable Catastrophe."
North Korea, which may have a handful of nuclear warheads, is a less likely potential terrorist source. The North Koreans might, however, be willing to sell nuclear material to the black market.
More dangerous, but less publicized, are research reactors with stores of highly enriched uranium. Some 20 countries have more than a bomb's worth of material at such sites. The most vulnerable are in former Soviet republics.
Al-Qaida's desire to obtain enriched uranium is well-documented. If they succeed, "we have significantly underestimated the ease of manufacturing a crude but effective nuclear weapon," warns the Monterey Institute's William Potter, co-author of a new book on "The Four Faces of Nuclear Terrorism."
I asked the experts a second question: Does the allocation of counterterrorism resources reflect their list of likely nuclear suspects?
The universal answer was a loud no.
Programs to secure bomb-grade material in Russia and to upgrade security at weapons storage sites have either stalled or remained at pre-Sept. 11 levels.
"In the two years after 9-11, fewer potential nuclear weapons have been secured in Russia than in the two years before," says Allison, a former senior defense official.
Pakistan's cooperation is highly limited; U.S. officials have not even been allowed to directly question Khan.
The Department of Energy has spearheaded a new initiative to gather up stores of enriched uranium around the world. But "outside the DOE, I don't have the impression that the Bush administration recognizes the urgency of the problem," Potter says.
Why isn't more being done? One reason is denial -- not only here but also in Russia. Many experts downplay the ability of Islamic terrorists to build a bomb or to steal one.
The Sept. 11 commission report talks of "the failure of imagination" on the part of our law enforcement and intelligence community to grasp that threat. When it comes to nuclear terrorism, the same "failure" is at work today.
-- Daniel Sneider is foreign affairs columnist for the San Jose Mercury News.