Here is an interesting essay by Harvard law professor Jack Goldsmith. Key paragraphs:

A final explanation for the congruence between Obama and Bush policies is that governing is much harder than campaigning. The presidency invariably gives its occupants a sober outlook on problems of national security. The "responsibilities placed on the United States are greater than I imagined them to be, and there are greater limitations upon our ability to bring about a favorable result than I had imagined them to be," said President John F. Kennedy, nearly two years into his presidency. "There is such a difference between those who advise or speak or legislate, and between the man who must select from the various alternatives proposed and say that this shall be the policy of the United States. It is much easier to make the speeches than it is to finally make the judgments."

President Obama has gone from a legislator and presidential candidate to the commander in chief wholly responsible for the nation's safety. He now reads the same threat reports as President Bush and confronts the same challenge of stopping Islamist terrorists who hide among civilians and who want to use ever-smaller and more deadly weapons to disrupt our way of life. He also faces the same paucity of truly useful information about the enemy and the same hard tradeoffs between liberty and security. And he knows that the American people will blame him and no one else if the terrorists strike. "The whole government is so identified in the minds of the people with [the president's] personality," said William Howard Taft, "that they make him responsible for all the sins of omission and of commission of society at large." The intense personal responsibility of the president for national security, combined with the continuing reality of a frightening and difficult-to-detect threat, has unsurprisingly led President Obama, like President Bush, to want to use the full arsenal of presidential tools.

You may recall that I made the same point many times in this blog. Power chastens. One of the perquisites of powerlessness is irresponsibility. It is why so many academics (legal, philosophical, and otherwise) defend an absolute prohibition of torture. If they had to decide whether to torture—and to accept the consequences of the decision—they would drop their absolutism in an instant.