He's in his second year as president, and he has discovered that even with all the powers of office, he can't do everything he wants to do, such as remake America. Doing stuff is hard. In the past, prosaic work has held little appeal for Obama, and it's prompted him to think about moving on.
Begin with his first serious job, as a community organizer in Chicago. Obama got a little done, but quickly became frustrated with small achievements. "He didn't see organizing making any significant changes in things," Jerry Kellman, the organizer who hired him, told me in 2008.
What Obama wanted was political power, and that is what sent him to Harvard Law School. "He was constantly thinking about his path to significance and power," another organizer, Mike Kruglik, told me. "He said, 'I need to go there (Harvard) to find out more about power. How do powerful people think? What kind of networks do they have? How do they connect to each other?'"
Out of law school, Obama did some civil-rights work in Chicago before running successfully for the Illinois Senate in 1996. Almost immediately, Obama began "chafing ... at the limitations of legislating in Springfield," in the words of a Washington Post profile.
Easily bored, and with a growing sense of dissatisfaction, he set his eyes on the House of Representatives, unsuccessfully challenging Rep. Bobby Rush in 2000. In 2002, he began his campaign for the U.S. Senate.
He won in 2004, but the Senate proved unsatisfying, too. By mid-2006, Majority Leader Harry Reid "sensed his frustration and impatience, had heard rumblings that Obama was already angling to head back home and take a shot at the Illinois governorship," write Mark Halperin and John Heilemann in the new book "Game Change." Reid knew "Obama simply wasn't cut out to be a Senate lifer."
According to the book, the majority leader invited Obama to his office for a talk. "You're not going to go anyplace here," Reid told Obama. "I know that you don't like it, doing what you're doing." Reid suggested that Obama run for president. Obama had been a senator for all of 18 months at the time. Soon after, he was off and running.
What drove Obama was not just ambition, although he is certainly ambitious.
As he became frustrated in each job, Obama concluded that the problem was not having the power to do the things he wanted to do. So he sought a more powerful position.