Senator Barack Obama served members of the press birthday cake on his campaign plane yesterday. (Photo: Alex Brandon/Associated Press)

Monday was Barack Obama’s birthday, his 47th, but you would hardly have known it from the schedule he kept. He left his home in Chicago early in the morning to fly to Lansing, Mich., to deliver a long speech on energy policy.

After interviews with the local press there, he then flew to Boston for a “birthday celebration and dinner” that was, in reality, a fund-raising event attended by 850 people, including Senator John Kerry, the 2004 Democratic nominee for president, and singer Harry Connick, Jr. Then it was back on the plane for a night flight to Youngstown, Ohio.

But the mother of a reporter traveling with Mr. Obama had baked him cookies to mark his birthday, and about midway through the flight to Youngstown, Mr. Obama came to the middle of the plane, where the traveling press sits, to thank him for the gesture. That, of course, triggered the question: how does it feel to be 47?

“Ancient,” Mr. Obama replied. Can you imagine being 71? someone else asked, referring to the age of Mr. Obama’s opponent, Senator John McCain, who is also an August baby, born August 29, 1936. Mr. Obama didn’t rise to the bait. He simply smiled and said “no comment.”

Other chitchat followed. Mr. Obama talked about the blue tie his daughters had given him as a birthday gift (“everybody seemed complimentary about it.”) He mentioned spending a relaxed Sunday with the godparents of his daughters. “I just sat in a lounge chair and drank a beer,” he said and “for about two hours” just watched his daughters dance as they listened to Beyoncé and the Jonas Brothers on their iPods. “It was really cool.”

But the reporters who travel with Mr. Obama complain that they rarely get to have informal exchanges now that he is the presumptive Democratic nominee for president. So almost inevitably, the conversation turned gradually to weightier matters: his energy policy, reflections on his recent overseas trip, and the politics of last week’s effort by the McCain camp to paint him as a shallow celebrity who has more in common with Britney Spears and Paris Hilton.

“We thought that the trip accomplished what I wanted to accomplish, which is to give the people back home some sense of how I would operate internationally, the kind of vision I want to project about America to the rest of the world,” he said, “and make an assessment of Iraq and Afghanistan.”

As for the comparisons with the dysfunctional blonde celebrities (and the accusations of ‘playing the race card’ which Mr. Obama did not mention but were also much in the news), “last week I think was just a series of distractions,” he said. “It felt, I guess, like a squid that sent out ink.” He added: “The question for me is always how do you avoid getting pulled into that kind of politics without getting slapped around.”

Of Mr. McCain, he said that “he brought in a team that is very adept at this kind of politics. This politics has been successful in the last two elections in terms of getting people elected. It has not been successful in governing or bringing the country together to tackle big problems. So we are in a constant internal debate about how we respond to this.”

Regarding himself and his own team, “we’re not always perfect,” he acknowledged. “You make mistakes, sometimes you get caught up in the adrenaline of the process.”

There are, he went on, clear differences between him and Mr. McCain on issues such as taxes, energy and health care. But “my sense was that last week wasn’t about any of that stuff,” he said. “It was all about seeing if they can slap on to me a certain caricature that will help carry them through the election.”

The news of the day had been Mr. Obama’s decision to reverse his opposition to tapping into the Strategic Petroleum Reserve. He defended that move as a harmless way to nudge down gasoline prices.

“I historically have been very hesitant about that. But the idea of a swap actually I think has merit in terms of just short-term effect on prices. I offer no sort of suggestion that in any way that it is going to make a long-term impact. Demand worldwide has gone up, and supply has flatlined at best. We’re going to have to make some enormous adjustments,” and not just in energy policy, but also in health care, education, infrastructure investment and the budget.

“The way I describe it is that we’ve got a ship that over the next six to nine to 12 months, we’ve got to steer it to port because it’s taking on water,” he said. “We’ve got to be real concerned about a big wave hitting that ship. Once we get it into port, though, we’ve got to fix the hull.”

After 20 minutes, Mr. Obama seemed to have had enough. “We gotta go get the cake,” he said. But there was one last question, about the wisdom of his decision to take a short vacation at the end of this week.

“I’ve been going pretty much straight for 18 months now,” he replied. “I have not seen my grandmother, who I usually see every year,” and besides her, “those little girls need a little love. As does Michelle, I think. So we’re going to take the time.”

With that, he was gone. But he returned in a few minutes to distribute pieces of yellow cake, which, as he had promised, was “pretty decadent, with lots of frosting.”