Oprah: I'm surprised you were so candid about having used drugs.

Barack: I think the biggest mistake politicians make is being inauthentic. By writing about my mistakes, I was trying to show how I was vulnerable to the same pitfalls as American youth everywhere.

Oprah: Right. Is there anything about Washington that frightens you?

Barack: The things that concern me have to do with my family. I want to make sure we're spending enough time with one another and drawing a circle of common sense around what can be a very artificial environment. That's where I rely so much on Michelle.

Oprah: What do you know for sure?

Barack: I know that I love my family. I know that people are fundamentally good. I know that, in the words of Dr. King, "The arc of the moral universe is long but it bends toward justice." I know that there is great suffering and tragedy in the world, but ultimately, it's worth it to live.

Oprah: Do you think you'll be the first black president?

Barack: A bunch of people have started talking about that. Listen, if you're in politics, at a certain point you think about where to take your career. But at this stage, it's way too premature. Politics is a marathon. So many things can change. You can't plan 12 years ahead. But what I will say is this: We can win the race we're in now. I think I have the aptitude to be a terrific United States senator. And if, at the end of my first term, the people of Illinois say, "This guy's been serving us well," then I'll be in a strong position to have a lot of influence in this country for a long time to come—whether or not I'm president.