The other existential threat candidates must confront

It now seems within the realm of possibility that over the next few years, the most important nuclear arms control treaties -- negotiated among the world's nuclear powers over nearly four decades of painstaking diplomacy -- will have expired or been eliminated. This would open the floodgates to a 21st century arms race that could be far more chaotic and dangerous than what threatened the world following World War II.

Given this reality, we need to do everything in our power to re-establish agreements that will keep the world's nuclear arsenal in check. With a presidential election on the immediate horizon, each candidate's approach to the issue of nuclear weapons needs to be a centerpiece of discussion, not a mere debate question that is answered with the standard response that limiting access to nuclear weapons -- particularly in key countries like Iran -- is important. We must take seriously the severity of the threat we could face.