That ubiquitous scrutiny makes it even more important that a president remain resolute and clear-eyed about his mission. It is critical that he look bigger than his critics. And, as is always the case in politics, that he project optimism about his leadership.

It is in that regard that Obama has faltered in the days since the story of the misdeeds at the IRS broke, cranking up the political and media intensity. One can argue whether the White House was too slow to respond and stanch the bleeding. In some ways, that is a question for lawyers, who can debate how cautious a president must be in responding to such allegations. But it is hard to disagree that this president has lost his footing in the way he presents himself.

Optimism is a vastly underrated component of a successful presidency. Voters tend to reject presidents who are dour or who talk of malaise. They reward those like Franklin Roosevelt and Ronald Reagan, who offer hope and grand promises. Obama must know this. It was in many ways the basis of his improbable campaign success in 2008. And even today, beset by controversies and investigations, he pays it rhetorical service. But the message is decidedly mixed.