WASHINGTON (AP) — White House chief of staff Denis McDonough was ready to vent.

"I've had too much humble pie," he fumed, striding into a top aide's West Wing office. "That was the last slice. I'm full."

McDonough had just finished another hand-holding meeting with health care advocates anxious over the disastrous rollout of the health care law. For weeks, President Barack Obama and White House officials had been apologizing for and promising fixes to a faulty website and an unmet promise to insurance holders that they could keep their policies.

McDonough's message: It was time to change tactics, quit lamenting the problems and start emphasizing the benefits of the health care overhaul.

When Obama assembled his second-term team last January, his new chief of staff promptly put his energetic stamp on things. He increased White House outreach to lawmakers, worked to rebuild relations with the Cabinet and stepped up contacts with business leaders.

Ten months later, McDonough is trying to manage one of the roughest patches in Obama's presidency as the White House labors to explain how the president got blindsided by the problematic enrollment launch of his health care law. As the president's gatekeeper, McDonough is at the center of the maelstrom, the man charged with deciding what the president needs to know and when.

With his periodic treks to the Capitol and his credentials as a former Senate staffer, McDonough has built a deep reserve of good will among lawmakers from both parties. But the botched health care rollout has angered many Democrats who wonder why the White House did not see the trouble coming.

"This is so important to the president, this is his signature issue," said Rep. Elijah Cummings, the top Democrat on the Committee on Oversight and Government Reform. "Not only is it his signature issue, it is the signature issue for the Republicans on the negative side. That's a hell of a combination.

"If you have something that significant, that's the kind of thing I would think I'd have somebody sleeping with it day and night. When they go to the bathroom, they're on the cell phone talking about it. When they go to sleep, they dream about it."

McDonough is now holding evening meetings every day with key players in the health care rollout, offering support even as he holds agency leaders accountable.

"We went straight into problem solving," he said last week during a stroll on the White House South Lawn. "We knew that going into this, that no plan survives first contact. We knew that we would be confronted with challenges along the way.

"We are focused on getting it working, absolutely, and we're making good progress on that."

Indeed, how the health care website performs on Dec. 1 and beyond will be an acid test of McDonough's leadership and crisis management.

Still, the debacle has been damaging. Obama's public approval and his ratings for honesty and strength have sunk, and his personal favorability numbers have been leaning negative.

All that has raised a panic with Democrats, who fear the consequences in next year's midterm elections. Aware of the anxieties, McDonough meets every other week with more than a dozen Democratic senators up for re-election in 2014. And while aides say he is devoting 70 percent of his time to health care issues, McDonough says he's also focused on advancing the president's economic agenda, the overhaul of immigration laws and working to address college affordability and climate and energy issues.

Friends and colleagues say McDonough has taken much of the blow himself.

"Denis takes everything personally. Nobody is going to be harder on Denis than himself," says his friend Ben Rhodes, a deputy White House national security adviser. "He was angry, frustrated, all of the above. If there is a problem, it is his personal mission to fix it, even if it is beyond his direct capacity to do so."

Of all the chiefs of staff who have worked for Obama, McDonough, 43, has the closest relationship with the president. Until Obama named him chief of staff in January, he had been a foreign policy specialist and had served as Obama's deputy national security adviser. Intense and to-the-point, he is more like Obama's first chief of staff, now Chicago Mayor Rahm Emanuel, than his more laidback predecessors Bill Daley and Jack Lew.

He has been at the center of all recent White House eruptions, from seeking congressional approval for military action against Syria to revelations the National Security Agency had spied on allied leaders. Both created significant political and international problems for Obama. He also held the line on Obama's vow not to negotiate with Republicans over the nation's borrowing authority, ultimately forcing Republicans to drop demands for concessions in exchange for a short-term increase in the debt ceiling.

"In my last job I spent a lot of time in the Situation Room, hours and hours during the day where you're making policy and working collaboratively with your colleagues and you can afford to, in that environment, not to be out reacting to news of the day," he said. "This job confronts you with news of the day every day, so the challenge is making sure that we're appropriately responding to and getting in front of news of the day without letting it push you off the president's long-term objectives and strategies."

Nothing has risen to the magnitude of the disastrous start of health care enrollment.

"It's the nature of the job. There is a lot of focus on who's responsible, who did what wrong. I think the bottom line is he has the responsibility of getting it right," said Patrick Griffin, who served as legislative director for President Bill Clinton and is part of a group of former Clinton aides with whom McDonough regularly consults. "And whether that was a problem in the agencies or consultants or the White House, there is no alternative, all that muck runs right to him."

McDonough is a fierce defender of the president, known during his national security days for vigorously challenging reporters. In a recent meeting with Democratic senators, a participant in the room said, he had a feisty exchange with Sen. Tom Harkin, D-Iowa, over a fix the president had proposed to the health care law.

Six-foot-two and lean, McDonough, 43, rides his bike to work in the early morning darkness two or three times a week from his home in the Washington suburb of Takoma Park, with his Secret Service detail riding along.

Regularly on the phone — or "the blower" in the patter he has introduced to the White House — McDonough has worked to build congressional relationships that had either been nonexistent or had soured during Obama's first term. Building from past acquaintanceships with Republican Sens. John McCain and Lindsey Graham, McDonough has reached out to Republicans, joining them for dinner, cocktails and personal sessions.

McCain says McDonough "has facilitated communications between Republicans and the White House in a way that none of his predecessors did." McCain, who participated in dinners Obama held earlier this year with various Republican senators, added: "This president does not like to spend a lot of time with people. ... By those dinners that he had — and I recommended to the president that he do more because all second-term presidents are now looking at their legacy — that was helpful."

But the talks and dinner have not helped avoid bitter confrontations like the one that resulted in a partial government shutdown.

"What's the benefit of that or what's the success?" McDonough asked of the recent outreach. "I think the answer to that is, it's incomplete."