WASHINGTON - It didn't take long for Barack Obama - for all his youth and inexperience - to get acclimated to his new role as the calming leader of a country in crisis.

"I feel surprisingly comfortable in the job," the nation's 44th president said a mere two weeks after taking the helm.

"The challenges are big," a sober Obama added, underscoring the foreign and domestic problems he inherited Jan. 20. "But one thing that I'm absolutely convinced about is that you want to be president when you've got big problems. If things are going too smoothly, then this is just another nice home office."

Over nearly 100 days as president, Obama has applied the same "no drama" leadership and calculated approach to governing that he did to campaigning.

As an audacious candidate, Obama meticulously built a powerhouse organization and fundraising juggernaut to engineer his victory. As a fledgling president, he similarly has mapped out a big-risk agenda that he's methodically begun to execute, keeping to the discipline that has been a hallmark of his life.

Rookie jitters? Far from it.

Confident almost to a fault, he could seem aloof, even arrogant at times in the campaign. He's kept that focused attitude in the White House, while exhibiting few flashes of any off-putting, self-important tone.

Perhaps that's because he's reached the pinnacle of his political ambition. Perhaps it's because anxious times of war and economic crisis demand a calm demeanor. Perhaps it's the sheer weight of the office and the urgent tasks.

Whatever the reason, Obama has seemed extraordinarily at ease as president from the day he took office - after a campaign in which he made a once skeptical electorate comfortable with the notion that a black, 47-year-old, first-term senator with limited experience could take over as the leader of the free world.

"He became presidential almost immediately. Physically as well as rhetorically he transformed himself," said American University professor James Thurber, an expert on the presidency. He said Obama had little choice but to dive in and start governing, given the full plate of issues. But, Thurber added, "He also did it with real skill and confidence that you wouldn't necessarily expect from someone who just walked in the door."

For the past three months, Obama has spoken in firm, yet soothing tones.

Sometimes he has used a just-folks approach to identify with economically struggling citizens. He has displayed wonkish tendencies, too, appearing much like the college instructor he once was while discussing the intricacies of the economic collapse. He has engaged in witty banter, teasing lawmakers, staffers, journalists and citizens alike. He has struck a statesmanlike stance, calling for a renewed partnership between the United States and its allies.

He also has steamed with anger, berating American International Group Inc. executives who granted enormous bonuses even while accepting federal bailout money. He has gone after lawmakers who refused to support the $787 billion economic stimulus package.

He has shown contriteness, saying "I screwed up" in the failed nomination of former Sen. Tom Daschle, D-S.D., as health secretary. He has shown irritation at criticism, snapping to a reporter, "I like to know what I'm talking about before I speak."

He also has let it be known he hasn't forgotten how politics works. "If I don't have this done in three years, then there's going to be a one-term proposition," Obama said a few weeks into his presidency, linking the economic recovery with his political fate.

Stylistically, this is a careful president who uses a teleprompter even during news conferences and presides over a White House that scripts his public appearances. For all his caution, Obama has made a few errors, including saying he thinks he bowls like a competitor in the Special Olympics.

So far, the public has liked what it's seen.

An Associated Press-GfK poll shows that most people in the U.S. consider their new president to be a strong, ethical leader who is working for change as he promised in his campaign. Obama's job approval rating stands at a healthy 64 percent. For the first time in years, more people than not say the country is headed in the right direction, the poll says.

Mindful of Obama's high popularity and, thus, the media's hunger for any details about him and his family, the White House has gone to great lengths to make sure he's visible. He's granted numerous television interviews and was the first president to jaw with Jay Leno on NBC's "Tonight" show. He tends to hold at least one public event a day to ensure news coverage.

He plans to mark his 100th day on Wednesday by traveling to St. Louis for a speech, then returning to Washington for his third prime-time news conference since taking office.

People don't seem to mind all that exposure. The AP-GfK poll found most people say he's on TV just the right amount, while just over one-quarter say he's on too much.

Overall, Obama seems unflappable.

"Humbled but not daunted," is how adviser David Axelrod puts it.

The senior White House adviser downplays any notion of cockiness. "I just don't think when you have two wars and an economy in turmoil you want a conflicted president. I think you want a thoughtful president, you want a president who is willing to consider all the options," Axelrod said. "You also want a confident president, someone who is willing to make decisions and live with the consequences of those decisions, and that is the kind of president he is."

During the campaign, advisers privately acknowledged that overconfidence might leave Obama vulnerable. He made a string of comments that were, to some extent, joking and self deprecating, almost as if he didn't take the hubbub around his candidacy too seriously. Still, others saw arrogance.

At one point, Obama the candidate said, "To know me is to love me." At another, he joked that when he finished speaking "a light will shine down from somewhere. ... You will experience an epiphany. And you will say to yourself, 'I have to vote for Barack.'"

These days, remarks like those are rare for Obama the president, though not entirely gone.

Asked during a February interview with US Weekly whether he wore boxers or briefs, the new president said: "I don't answer those humiliating questions. But whichever one it is, I look good in 'em!"