WASHINGTON (AP) — It was always his mess to clean up. That's what Americans expect from their presidents.

And so on Day 37 of what is now the worst oil spill in U.S. history, President Barack Obama took responsibility in the only obvious way left.

Unequivocally.

In case you were wondering who's responsible, I take responsibility," Obama said at a news conference arranged to make that very point. "It is my job to make sure that everything is done to shut this down.

No more White House parsing about how BP PLC is legally responsible for plugging the leak and paying the cost, even though that remains accurate. Obama knew that his own accountability was needed for the angry Gulf Coast communities, for an administration struggling to nail its message, for himself.

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And once you're in, no point being subtle.

In language presidents normally reserve for the burden of sending troops to war, Obama said of the oil spill: "This is what I wake up to in the morning, and this is what I go to bed at night thinking about." At a time when Obama is juggling a host of nettlesome problems — the wars, the economy, Mideast peace — he pushed them all behind this one, saying his government has been "singularly focused" on fixing the spill.

This is what comes with the job, and the sympathy of voters is not everlasting. Presidents get hired to fix problems they have never even contemplated.

When a government loses its credibility with the people, the blow can be devastating. And although bigger issues than politics are in play — mainly, the enormous destruction to the waters and wildlife — this was clearly a consequential moment for Obama.

A new Gallup poll finds that more than half those surveyed thought Obama was handling the crisis response poorly. That is despite all the crews and aid and equipment Obama's team had dispatched, all the times his incident commander and his interior secretary and his West Wing advisers made the case to the media.

And so Obama stepped in.

He resurrected a buck-stops-with-me theme he has used before, most notably after a would-be airliner bomber exposed security lapses on Christmas Day. Obama could not seem to claim ownership enough, declaring on Thursday: "My job is to get this fixed.

He tried to put the leadership questions behind him.

The American people should know that from the moment this disaster began, the federal government has been in charge of the response effort," Obama said before a reporter could even ask him about it.

No one in his administration had made that statement so plainly or prominently.

The reassurance, as needed as it may have been, does not change two underlying realities.

The first is that no amount of words, no presidential attention like Obama's trip to the Gulf on Friday, will replace what people want: results. And that is a much more far-reaching challenge of plugging the leak, cleaning up the oil, holding a big oil company responsible and preventing deep water rigs from sinking in disaster.

The other reality is that the government, in fact, is not in charge of the incident the way people want.

It cannot push BP out of the way and take over the operation of fixing a busted, gushing well a mile below the sea's surface. The most powerful government in the world is simply not equipped to do that.

One of the more revealing, if overlooked, moments at Thursday's news conference came when Obama recalled a discussion in the Situation Room. He asked Defense Secretary Robert Gates and Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, whether the military had any assets that the oil companies lacked to deal with the crisis.

There were none. "We do not have superior technology when it comes to dealing with this particular crisis," Obama said. Understandably, he suggested that the federal government should start examining whether it should develop some.

Obama had his defensive moments. "Those who think that we were either slow on our response or lacked urgency don't know the facts," he said.

Yet he was calm about it and would not let his tone of accountability get lost.

Yes, he said, his government has messed up, such as by misjudging the oil industry's ability to cope with the worst-case scenario.

Yes, he understands the hardship for a Gulf region with fresh memories of Hurricane Katrina.

The methodical president was plainspoken.

Understandably, people are frustrated because, look, this is a big mess coming to shore," he said.

To connect in real terms, he even pulled in a story of his 11-year-old daughter.

When I woke this morning and I'm shaving and Malia knocks on my bathroom door and she peeks in her head and she says, "'Did you plug the hole yet, Daddy?'" Obama said.

That was Obama's most effective moment, said Kevin Sullivan, the former communications director for President George W. Bush. "It did make it personal," Sullivan said. "In addition to conveying that 'We're on the case,' the White House wanted to convey that it cares about the people involved.

Still, Obama could not pass up a chance to plug his policy agenda. He said the risky, costly extent to which companies are drilling for oil underscores the need for Congress to take up a bill of alternative energies.

If nothing else, this disaster should serve as a wake-up call that it's time to move forward on this legislation," Obama said.

Make that a wake-up call in more ways than one.

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EDITOR'S NOTE — Ben Feller covers the White House for The Associated Press.

Copyright 2010 The Associated Press.