The BP spill won’t destroy Barack Obama’s presidency. It won’t even significantly dent his standing in polls, if current trends hold. But it should mark the end of a period of unbridled liberal presumption that began with his rise in 2007.

In his new book, “The Icarus Syndrome,” author Peter Beinart writes of “hubris bubbles” that infect American foreign policy after successes. In the domestic arena, liberalism has been riding its most expansive hubris bubble since Lyndon Johnson modestly declared on the cusp of the Great Society, “These are the most hopeful times since Christ was born.”

Those millennial expectations returned with the honeyed words of Obama. He promised to heal the planet and turn back the tide of rising    oceans, and liberals believed him. So when a mere 35,000-60,000 barrels of oil a day gushing from the bottom of the Gulf of Mexico produced a crisis beyond his control, they lashed out in frustration.

Obama had to get angry! He had to declare war — and without U.N. authorization — on the spill! He had to use the crisis to push through cap-and-trade! And when Obama followed all the stage directions set out for him by his formerly worshipful journalistic boosters, they still felt empty and unsatisfied because, well, there are really no presidential words or emotions that can make up for miles of soiled coastline.

Obama’s much-touted Oval Office address on the Gulf got instantly panned by MSNBC’s analysts in a shocker equivalent to Pravda’s best pundits dismissing a Brezhnev five-year plan. They complained that the speech was trite and vague, as if that made it any different from most of Obama’s gaseous oeuvre. His call to arms on behalf of a new green economy was particularly tinny for two reasons.

One, Democrats have tapped out the public’s appetite for expensive, impossibly complex new government programs. They forced their will on health-care reform, but it remains unpopular. No one believes Obama has the votes for a far-reaching plan to remake the energy economy, so he stuck to the same bromides repeated by every president since Jimmy Carter.

Two, the Gulf Coast is not a reassuring backdrop for a stirring summons to more government action. Obama cited the production of planes and tanks during World War II and the Apollo mission to the moon as evidence of government’s awesome proficiency. But those were relatively straightforward feats in manufacturing and rocketry from 70 and 40 years ago, respectively.

The largest spill in U.S. history was going to be a chaotic mess regardless of who was president, because it was unprecedented, vast and complex. The liberal chest-pumping about declaring “war,” or even a “holy crusade,” on the spill speaks to an impatience with the inevitable delays and inefficiencies of a government operating — in league with a hated company — in confusing circumstances.

Welcome to soggy reality. The great liberal disenchantment is the realization that it’s beyond Obama’s powers to turn back an oil spill, let along the tides. He’s just a president, and not even a particularly good one.

Lowry is editor of the National Review.