The Obamas' biographer on the introverted president, the strength of Michelle and the stains the Bush family left on the White House carpets

One of the things we learn from your book, The Obamas: A Mission, A Marriage, is not only how the first couple make their marriage work but that Michelle Obama owns a pair of $515 designer trainers…

I know! It's kind of astonishing.

The lifeblood of any piece of reportage is in this kind of telling detail; how difficult was it for you to get that kind of access to the White House?

Well, I spent a lot of time in the White House in the public areas where reporters are allowed to go, but I spoke to people about the private quarters as well. Some of the things I learned were small, novelistic details. For example, the fact that there were still pet stains on the carpets from the Bush cats when the Obamas moved in. I feel the White House is almost a character in this book. What does it mean to live in this place? It's a home, but it's also an office and a military compound and – by the way – it's also a terrorist target.

It interested me that it has no private exit or entrance for the family. I was in the White House a few months ago, standing in the Diplomatic Room and Sasha [the Obamas' youngest daughter] appeared with her grandmother. She was coming in from school and the staff just nodded and smiled, but I was a bit embarrassed that she had to run past a reporter to get home. It must have felt a little uncomfortable.

You are scrupulous in the book about not proffering a personal opinion of the Obamas. But who would you rather be stuck in a lift with – Barack or Michelle?

I find the Obamas incredibly compelling because I've been covering them for five years. It's less about liking or not liking them than about following the drama of the story.

Is President Obama as charismatic as everyone says he is?

In Washington, he's considered quite an introvert. A few days after he became president, he hosted a Superbowl party. He greeted everyone politely but, in essence, he wanted to watch the game as normal. He said to me later it was a point of pride for him that he wasn't a politician who stood there and shook hands. That has not gone across well in Washington because most presidents are schmoozers and he is not. Many people believe that Michelle Obama has the charisma.

One of the most interesting chapters in your book deals with the discomfort faced by the Obamas when they realised most of the staff in the White House are of African-American descent. Has their tenure improved race relations in the US?

It's way too early to tell. When I wrote the book, I felt that that question was still beyond our grasp. The question I focused on was: what is the day-to-day experience of being the first African-American president and first lady? For example, when the invitation came for Michelle Obama to appear on the cover of Vogue, her advisers were split by race. The African-American advisers really wanted her to do the cover because not that many African-American role models had done so. On the other hand, the white advisers were far more cautious because the country was in terrible economic straits and Vogue is a pure luxury magazine – the newsstand price alone is something like $5. In fact, she chose to do the cover and there was very little criticism. To me, that is one tiny look into the real mosaic of what's going on.

Have the Obamas read the book?

I don't know. I haven't heard back.

You say in your acknowledgements that you became a political reporter for the New York Times at the same time as you became a mother, did you ever find it hard to balance the two?

At one point during the 2008 campaign I got called up and screamed at by an Obama aide. It was 7pm and I'd just got home. My daughter was about two and she was sitting on my lap and she took control of the cell phone and began singing the Barney song down the phone: "I love you, you love me. We're as happy as can be." It was just surreal and kind of amazing on her part. In a way, it was the best thing to say to an over-agitated campaign aide.

Your book makes it clear the Obamas have distinct personalities – you say he's more cerebral, finds it difficult to connect with the public, whereas she's warmer and more feisty. Do you think it's the differences rather than the similarities that make their marriage work?

Absolutely. I don't think he would be president without Michelle Obama because she's the one who connects him with other people.

Can a marriage ever truly be one of equals when one partner is the leader of the free world?

The answer to that is in the book. On the one hand, Michelle Obama comes to the White House and really has to play second fiddle in a job that is not well-defined. But I watched her find ways to assert her power. This is a story of a woman who, at the start, was put in a very retro role. Her challenge is to find ways to be powerful. In the White House, she goes from not having that much power to having so much internal leverage because she's so much more popular than he is.

Did you see parallels in your own marriage with the Obamas' partnership?

I guess there were things about the Obamas I discovered that I do think are universal to marriage. I found it very interesting in my reporting that their most difficult periods in the White House almost never seemed to coincide. When one was down, the other one was holding it together. In my experience, that's true of marriage generally. There's some emotional delegation of power.

Do you think, as some are saying, that Obama will be a one-term president?

I've learned that the best political reporters never make predictions! I guess the question I have is whether he has the capacity to reboot… to reformulate the idea of why he wants to be president because the 2008 formula no longer works. He needs to spell out a new, compelling and realistic vision for the country.

Have you met Bo, the White House dog?

Yes. Getting an "interview" with Bo is far easier than with the Obamas. He becomes a kind of substitute because he runs around the White House all the time in the corridors. He's the perfect ambassador for them because you can rub your hands all over Bo and he's perfectly happy, whereas the Obamas like to protect themselves.

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