This column will be my last “Letter From Ground Zero.” The series will be succeeded by another, “Crisis of the Republic.” Until recently it seemed possible to trace the main developments in the Bush Administration’s policies back to that horrible, fantastical day in September 2001, as if following an unbroken chain of causes and effects. Now it no longer does. The chain is too entangled with other chains, of newer and older origin.

The war against Afghanistan, where Osama bin Laden had his headquarters and support from the ruling Taliban, was, for better or worse, a clear response to the attack on the United States. The Patriot Act and the reorganization of the national security apparatus likewise were responses to September 11. But with the launch of the Iraq War, the subject was already beginning to change. The political support for the war still flowed from 9/11, but the Administration was already veering toward other objectives. For one thing, we know that Secretary of Defense Donald Rumsfeld and others had wanted to attack Iraq since their first days in office, and, for that matter, even before. For another, the war proved to be a kind of test case of a far more sweeping revolution in American foreign policy, soon outlined in the White House document of 2002, the National Security Strategy of the United States of America, which set forth American ambitions for nothing less than global hegemony based on military superiority, absolute and perpetual, over all other nations. Many friends of this policy frankly and rightly called it imperial.

The Iraq test case has failed; in doing so it has tied down forces that otherwise might have been given further aggressive missions. The imperial plan stalled, as the nuclearization of North Korea without an effective American response, among other things, attests. Nevertheless, the Administration’s international ambitions had a scarcely less sweeping domestic corollary, for which no master strategic document was supplied: a profound transformation of the American state, in which, in the name of the “war on terror,” the President rises above the law and the Republican Party permanently dominates all three branches of government. That project had even less to do with 9/11 than did the Iraq War. Its roots can be traced at least as far back as the election of 2000, when the Supreme Court improperly interjected itself into the electoral dispute in Florida and a majority consisting of Republican-appointed Justices awarded the presidency to the man of their own party. Or perhaps we need to look back even further, to the attempt by the Republican-dominated Congress to knock a Democratic President out of office by impeaching him for personal misbehavior accompanied by a minor legal infraction. (If those standards were still in force, President Bush would have been impeached eleven times over by now.) Obviously, these events had nothing to do with 9/11 or the Iraq War. Their roots are older and deeper. To arrange all the new developments, domestic and international, under the heading “Letter From Ground Zero,” as if it all began with Osama bin Laden, would therefore be misleading. It would be a kind of lie.

For the series’ new title, I want to acknowledge a debt to Hannah Arendt, who in 1972 published a book of essays titled Crises of the Republic. My single-letter change in her title reflects a belief that today the many disparate crises of the past have combined into one general systemic crisis, placing the basic structure of the Republic at mortal risk. At the forefront of concern must be the question: Will the Constitution of the United States survive? Is the American state now in the midst of a transmutation in which the 217-year-old provisions for a balance of powers and popular freedoms are being overridden and canceled? Or will defenders of the Constitution step forward, as has happened in constitutional crises of the past, to save the system and restore its integrity?

The obvious precedent is Watergate. Then as now, the presidency became “imperial.” Then as now, a misconceived and misbegotten war led to presidential law-breaking at home. Then as now, a quixotic crusade for freedom abroad really menaced freedom at home. Then as now, the law-breaking President was re-elected to a second term. Then as now, the systemic rot went so deep that only a drastic cure could be effectual. Then as now, opposition at the outset consisted not of any great public outrage but the lonely courage of a few bureaucrats, legislators and reporters. Then it was the war in Vietnam; now it is the war in Iraq and the wider and more lasting “war on terror.” Then it was secret break-ins and illegal wiretapping; now it is arbitrary imprisonment, torture and, again, illegal wiretapping. Then it was presidential assertion of “executive privilege”; now it is a full-scale reinterpretation of the Constitution to give the “unitary executive” power to do anything it likes in “wartime.”

Of course, there are obvious differences. In the early 1970s, the opposition party controlled both houses of the legislature, which launched vigorous investigations and, eventually, impeachment proceedings. Now of course the President’s party controls the legislative branch and possibly (it’s still too early to say, given the traditional independence of the judiciary and its consequent unpredictability) the judicial branch as well. Then, the movement against the war had forced a decision to withdraw; now the antiwar movement is much weaker. On the other hand, when the crisis began back then, the President’s popularity was high; now it is low.

Yet what remains most striking and most surprising is the degree of continuity of the systemic disorder in the face of radical, galloping change in almost every other area of political life. After all, the cold war, which seemed at the time to be the seedbed of the Watergate crisis, ended sixteen years ago, in the greatest upheaval of the international system since the end of World War II. How is it, then, that the United States has returned to a systemic crisis so profoundly similar to the one in the early 1970s? By looking at external foes, are we looking in the wrong place for the origins of the illness? Is this transformation what a more “conservative” public now wants? Or is there instead something in the dominant institutions of American life that push the country in this direction? Those are some of the questions that will be taken up in “Crisis of the Republic.”