By all accounts, one of the distinctive features of the Bush Administration has been its relative intolerance for internal dissent. High-level officials have tended to settle on a particular course of action, quite early on, and to squelch rather than to promote discussion and debate within the White House or the administration more generally. The point applies to the Iraq war, of course, but to many other issues as well, including climate change, tax cuts, energy policy, the mortgage crisis, Hurricane Katrina, and much more. The Bush Administration's relative intolerance of internal dissent has extended to issues of fact, not merely issues of policy.
In this respect, the Bush Administration has been radically different from the Reagan Administration (which in many ways it sought to follow). I was privileged to serve as a lawyer in the Office of Legal Counsel under President Reagan, and even from my (lowly) vantage point, it was easy to see disagreement, debate, and contention within the White House. President Reagan was hardly indecisive, of course, but he did not stifle internal debates. On many issues at the intersection of policy and constitutional law, deliberation among contending positions was pervasive.
In the environmental context, a prominent example involves the problem of ozone depletion. After a vigorous debate, the White House favored extremely aggressive steps to combat ozone-depleting chemicals, and hence the United States took a leading role in the Montreal Protocol, which led the way toward phasing out such chemicals all over the world. (It is instructive to compare the Reagan White House on ozone depletion with the Bush White House on climate change.)
In investigating group dynamics, people often speak of "groupthink," but the term is vague and it's not clear whether it points to a testable hypothesis. A more helpful concept is "group polarization," which predicts that like-minded people, deliberating with one another, will typically end up in a more extreme point in line with their predeliberation tendencies. For example, French people who are suspicious of the United States will, after talking to one another, become more suspicious; people who tend to be racist will, after speaking with one another, become more racist. Common consequences of deliberation among like-minded types include (a) more extremism and (b) greater confidence.
In the Bush White House, the greater extremism, and the greater confidence, that followed from internal deliberation was often a product of group polarization and fueled by discouraging dissent. Of course, the Reagan White House didn't always make the right decision. But when it did well, it was often because of an internal system of checks and balances, produced by a diversity of view, and by a receptivity to those who challenged the prevailing orthodoxy.
There's a large lesson here for Senators Obama and McCain, and for thinking about their presidencies. Presidential candidates attract sycophants and worshippers. Because of their personal histories, Obama and McCain are unusually vulnerable to both. If they are to do well, they will need to avoid the Bush model and to build on the Reagan White House at its best. The executive branch has become so large, and so able to act for good or for ill on its own, that it needs to develop an internal system of checks and balances. Such a system is a critical safeguard against the forms of group polarization that have proved so damaging under President Bush.