RAY SUAREZ: The recent furor over President Bush's domestic intelligence program is the latest skirmish in a centuries-old battle over presidential powers in times of war. By letting government agents eavesdrop without court oversight, Mr. Bush joined a long list of presidents who've tested the limits of their war-time authority.

For a historical look at how executive powers have been wielded and its impact on governance, we're joined by Richard Norton Smith, director of the Abraham Lincoln Presidential Library and Museum in Springfield, Ill.; Ellen Fitzpatrick, a professor of history at the University of New Hampshire; and Andrew Rudalevige, professor of political science at Dickinson College and author of "The New Imperial Presidency: Renewing Presidential Power after Watergate".

Professor Rudalevige, either in method or degree are we in new territory with the Bush assertions of executive power?

ANDREW RUDALEVIGE: Well, I think we've pushed beyond old boundaries, but that is not to say these boundaries were very clearly drawn at any time throughout history. After Sept. 11, President Bush certainly was very aggressive in pushing forward an agenda of unilateral executive power arguing that this was justified, of course, by the crisis and also authorized by Congress, which after all after Sept. 11 passed a very broad resolution. Still, even before Sept. 11, the Bush administration had argued very forcefully that executive power had been reined in too far. I think you could argue that argument went too far, that presidential power throughout the post-war era anyway and even earlier than that had grown beyond what the framers certainly had in mind.

RAY SUAREZ: Richard Norton Smith, an aggressive agenda of unilateral power?

RICHARD NORTON SMITH: An aggressive agenda that no doubt the White House would say responding to events beyond anyone's imagination and in some ways the justification being put forth has its roots in Lincoln's Doctrine of Necessity 140 years ago.

Remember it was Lincoln who suspended habeas corpus, one of the most cherished rights of a free people, during the Civil War. He famously said, although it was sometimes necessary to amputate a limb to save a life, it was never wise to end a life to save a limb. In other words, the Doctrine of Necessity gave the president inherent power to temporarily suspend a clause of the Constitution in order to put down a rebellion by those who would trash the entire document.

Now that, obviously, can be a slippery slope and that is part of the debate that has been going on as long as there has been a Constitution and of which this is the latest chapter.

RAY SUAREZ: Professor Fitzpatrick, the president, in a recent news conference, cited Article 2 of the Constitution as the platform he was standing on, more or less, for these authorities, for his privileges in doing the kinds of things he was doing in wartime. What does Article 2 say and does he have a good case?

ELLEN FITZPATRICK: Well, the Constitution gives the president power as executive and as Commander in Chief and in the Federalist Papers, Madison made the point that one of the reasons for transferring power from the state government to the president, to the central government, was to protect against foreign enemies, to really protect the security of the country. But originally the notion of being Commander in Chief was not-- was explicitly divided from the notion that the president would decide when it was appropriate to wage war, that power very explicitly went to the Congress. So, the Constitution is very clear on this point.

What has happened historically, however, in times of war is that the Congress has ceded authority -- enormous authority in many cases -- to the president to take on powers during times of war because of this unusual situation and the importance of protecting the security of the nation. I think the historical context for what is going on now is really the expansion in the post-World War Two period of the national security state. It is the idea of national security, the doctrine of national security, that is being invoked now to justify a range of actions on the part of the Bush administration in the context of a proclaimed war on terror that has no endpoint.

RAY SUAREZ: Well you talked about how the Constitution expressly gives Congress the power to make war, but the United State's flag and its forces have gone a lot of places in the last 50 years without a declaration of war.

ELLEN FITZPATRICK: Yes.

RAY SUAREZ: Is this part of a general erosion of Congressional power?

ELLEN FITZPATRICK: It is certainly the case that very few times in American history, in fact, when military intervention has been undertaken has it happened as a result of a congressional declaration of war and increasingly in the post-World War Two period, what the idea of national security does is to put the United States in a state of permanent military readiness. It redefines foreign policy problems as threats to the security of the nation and it turns foreign policy goals or aspirations into necessities for the nation's survival and once that happens, what we've seen in the last 50-plus years, is that repeatedly the president invokes that idea, that doctrine, to take unilateral action and to consult the Congress belatedly, if at all.

RAY SUAREZ: Professor Rudalevige, is this a zero-sum game, that if the executive is gaining power it is almost, by definition, Congress that is losing it?

ANDREW RUDALEVIGE: Well, I don't buy that quite. Over time you have seen certainly the growth of a large American state, something that didn't exist in the 18th century, not only the military establishment that Professor Fitzpatrick talked about, but also a large executive establishment in domestic affair, a regulatory state, and as that grows, the government's power grows and the practical necessity of centralized leadership grows. The president has, in fact, been that person. Really under our Constitutional system, he is the only focal point of national leadership. But, that said, Congress needs to be defining the goals of that leadership, right? Where should it be going? In what direction should the country be going?

ELLEN FITZPATRICK: Yes.

ANDREW RUDALEVIGE: Congress has been, I think, asleep at the switch in recent years. The imperial presidency can really only be empowered by an invisible Congress and so, right now, I think we do have a zero-sum game. That's not a necessity.

RAY SUAREZ: Richard Norton Smith, is this a game of ebbs and flows as well? When the crisis passes, when the war is over, other forces in the country reassert their power and chip away at the expanded presidency?

RICHARD NORTON SMITH: Actually that is what's been the case for most of our history, Ray. If you look at-- If you look at the 19th century after the Mexican-American War and Polk presidency, the presidency was in many ways downsized, perhaps tragically in the years before the Civil War. There was a reaction after the Civil War to the enormous concentration of personal power that had flowed to the White House and you had a series of relatively weak presidents. After World War One in the 1920s, likewise, there was this reversal of power -- a lot of it back to Congress, a lot of it back to the states and the localities.

Picking up off what my colleagues have said, this is a game of Constitutional see-saw, what changed that dynamic really was the permanent Cold War. Just a few years after we witnessed the surrender of Japan and Nazis Germany, we undertook a whole different kind of foreign policy. It was called Communist containment. Harry Truman fought a war in Korea that he called a police action, not a war. Truman and Eisenhower and other presidents used the CIA and other instruments to overthrow hostile governments around the world -- all in the name of protecting the United States from this constant menace. It was, in effect, a permanent state of siege. And I do agree with Ellen, there are some parallels with the current war on terror.

But if I can say something heretical, we historians are complicit, to some degree. You know Teddy Roosevelt a hundred years ago had what he called his Stewardship Theory of the presidency, which said the president could do anything the Constitution did not explicitly prevent him from doing, and for most of the last century, most historians have almost reflexively celebrated the powerful, strong, energetic, agenda-setting, Congress-dominating president and, to some degree, the chickens have come home to roost.