By SHERYL GAY STOLBERG


WASHINGTON

THE CAPITAL BECAME flustered when, on his first full day in the White House, President Obama was photographed in the Oval Office without his suit jacket. There was, however, a logical explanation: Mr.Obama, who hates the cold, had cranked up the thermostat.

“He’s from Hawaii, O.K.?”said Mr.Obama’s senior adviser, David Axelrod, who occupies the small but strategically located office next door to his boss.“He likes it warm. You could grow orchids in there.”

Thus did a rule of the George W.Bush administration - coat and tie in the Oval Office at all times - come to an end, only the first of many signs that a more informal culture is growing up in the White House under new management. Mr.Obama promised to bring change to Washington and he has - not just in substance, but in presidential style.

Some of Mr.Obama’s work habits are already becoming clear. He shows up at the Oval Office shortly before 9 in the morning, roughly two hours later than his early-tobed, early-to-rise predecessor. Mr.Obama likes to have his workout first thing in the morning, at 6:45. (Mr.Bush slipped away to exercise midday.)

He reads several papers, eats breakfast with his family and helps pack his daughters, Malia, 10, and Sasha, 7, off to school before making the 30-second commute downstairs - a definite perk for a man trying to balance work and family life. He eats dinner with his family, then often returns to work; aides have seen him in the Oval Office as late as 10 p.m., reading briefing papers for the next day.

“Even as he is sober about these challenges, I have challenges, I have never seen him happier,”Mr.Axelrod said.“The chance to be under the same roof with his kids, essentially to live over the store, to be able to see them whenever he wants, to wake up with them, have breakfast and dinner with them - that has made him a very happy man.”

In the West Wing, Mr.Obama is a bit of a wanderer. When Mr.Bush wanted to see a staff member, the aide was summoned to the Oval Office. But Mr.Obama roams the halls; one day he turned up in the office of his press secretary, Robert Gibbs, who was in the unfortunate position of having his feet up on the desk when the boss walked in.

“Wow, Gibbs,”the press secretary recalls the president saying.“Just got here and you already have your feet up.”Mr.Gibbs scrambled to stand up, surprising Mr.Obama, who is not yet accustomed to having people rise when he enters a room.

Under Mr.Bush, punctuality was a virtue. Meetings started early - the former president once locked Secretary of State Colin L.Powell out of the Cabinet Room when Mr.Powell showed up a few minutes late - and ended on time. In the Obama White House, meetings start on time and often finish late.

When the president recently invited Congressional leaders to 1600 Pennsylvania Avenue to talk about his economic stimulus package, the session ran so long that Mr.Obama wound up apologizing to the lawmakers - even as he kept them talking, engaging them in the details of the legislation far more than was customary for Mr.Bush.

“He was concerned that he was keeping us,”said Representative Eric Cantor of Virginia, the Republican whip.“He said,‘I know we need to get you all out of here at a certain time.’But we continued the discussion. What are you going to say? It’s the president.”

If Mr.Obama’s clock is looser than Mr.Bush’s, so too are his sartorial standards. His aides did not quite know how to dress. Some showed up in jeans (another no-no under Mr.Bush), some in coats and ties.

So the president issued an informal edict for“business casual”on weekends - and set his own example. He showed up for a Saturday briefing with his chief economic adviser, Lawrence H.Summers, dressed in slacks and a gray sweater over a white buttoned-down shirt. Veterans of the Bush White House are shocked.

“I’ll never forget going to work on a Saturday morning, getting called down to the Oval Office because there was something he was mad about,”said Dan Bartlett, who was counselor to Mr.Bush.“I had on khakis and a buttoned-down shirt, and I had to stand by the door and get chewed out for about 15 minutes. He wouldn’t even let me cross the threshold.”

Mr.Obama has also brought a more relaxed sensibility to his public appearances. At the Capitol last month, he startled lawmakers by walking up to the microphones in a Senate corridor to talk to reporters, as if he were still a senator.

Mr.Obama’s daily schedule seems flexible. Mr.Bush began each day, Monday through Saturday, with a top-secret intelligence briefing on security threats against the United States. Mr.Obama gets the “president’s daily brief”on Sundays as well, though unlike his predecessor, he does not necessarily put it first on his agenda. Sometimes Mr.Obama’s economic briefing, a new addition to the presidential schedule, comes first.

If there is one thing Mr.Obama has not gotten around to changing, it is the decor. When Mr.Bush moved in, he exercised his presidential prerogative and asked his wife, Laura, to supervise the design of a new rug. Mr.Bush loved to regale visitors with the story of the rug, whose sunburst design, he liked to say, was intended to evoke a feeling of optimism.

The rug he installed is still there, as are the presidential portraits he selected - one of Washington, one of Lincoln - and a collection of decorative green and white plates. During a meeting with retired military officials, before he signed an executive order shutting down the prison at Guantanamo Bay, Cuba, Mr.Obama surveyed the Oval Office with a critical eye.

“He looked around,”said one of his guests, retired Rear Admiral John D.Hutson,“and said,‘I’ve got to do something about these plates. I’m not really a plates kind of guy.’”