The most powerful office on earth?

Tell that to Barack Obama as he waits this week to learn the fate of his landmark health care legislation, achieved through such fierce effort, meant to be a cornerstone of his legacy, and now utterly out of his hands.

Or as he watches the unfolding debt crisis in Europe, which could capsize the American economy between now and Election Day. He has minimal sway over how European leaders handle it. He has everything to lose if the job is botched.

Each month he braces for new Labor Department jobs numbers, knowing that his actions at this stage can’t influence them much before November and knowing, at the same time, that they could save or doom him.

On most fronts and in many ways, his presidency right now is an exercise in hoping and in holding his breath. He attained the most formidable station in the world only to experience a flimsy degree of control.

He’s hardly the first president to cross into this cruel limbo, where every hiccup in the domestic economy and spasm abroad is a potential death knell — or a mercy.

But how many presidents, at least in recent decades, have known something precisely like the Supreme Court’s possible erasure of the Affordable Care Act? How many have confronted a Congress this wholly paralyzed by partisan rancor and this steadfastly unyielding?

How many have done so after such an accelerated and charmed political prelude, during which they exerted such control over their own narratives?

While most politicians write their stories once they’ve laid some claim to the spotlight and are already operating in its skeptical glare, Obama did so years in advance, setting the stage long before he strode onto it. The first edition of “Dreams From My Father,” a framing device for the campaigns and speeches to come, was published in 1995. He wasn’t even an Illinois state senator yet.

It was an act of careful and considered self-definition, and with the publication of David Maraniss’s new biography of Obama earlier this month, we learned just how careful and considered. Obama tailored characters to suit his themes and invented a few details of his family’s past, saying that a step-grandfather was killed in combat against Dutch troops in Indonesia when he really, according to Maraniss, died in a fall from a chair as he hung drapes.

One of the most widely cited observations in Maraniss’s biography, “Barack Obama: The Story,” is that he had a “determination to avoid life’s traps.” He refused to let circumstances box him in; craved room to maneuver; kept his options open. In college he floated between cultures and political and social groups, studiously avoiding commitment. In the Illinois State Senate, he stood out in part for the frequency with which he voted “present” rather than yea or nay. He wouldn’t be pinned or pigeonholed.

And now? He’s beholden to lawmakers’ whims, buffeted by global winds, as much a spectator as an agent of the most important developments around him, a leader of the free world who follows the news like the rest of us. Against Obama’s wishes and will, his attorney general is investigated and excoriated by a House panel. His jobs bill languishes. Egypt charts a once unexpected course, electing an Islamist president. The Syrian government pursues a bloody crackdown against its people, ignoring the Obama administration’s protests.

At times he looks dazed, and flails. To focus his economic message, he gave an unfocused 54-minute speech on the apparent theory that the more sentences in the mix, the greater the odds of a keeper.

Less than a week later, he stepped up to a lectern at the end of a conference of world leaders in Mexico and rambled some more, whatever particular point he intended to highlight getting lost in a wonky, windy tutorial on the European economy. He stammered. Sputtered. Slowed down to the point where he almost went into oratorical reverse.

Much has been made of his recent executive decision regarding young illegal immigrants as an act of sheer political calculation. It may well be. But I wonder if there wasn’t an emotional motivation as well — if he wasn’t trying to find one small patch of ground on which he could have his unchallenged say and way.

Because the hell of his situation is its amalgam of full responsibility for so much and impotence in the face of most of it. I suppose that’s long been one definition of the presidency, but it has seldom fit as well as now. In the twilight of his first term, Obama is learning how unscripted history ultimately is. A second term may hinge on the nifty trick, not yet mastered, of projecting more command than he actually wields.