WASHINGTON — Long before the national press spotlight began to shine on every twist and turn of his life’s journey, Senator Obama had this to say about himself: “Junkie. Pothead. That’s where I’d been headed: the final, fatal role of the young would-be black man. … I got high [to] push questions of who I was out of my mind.”

The Democratic senator from Illinois and likely presidential candidate offered the confession in a memoir written 11 years ago, not long after he graduated from law school and well before he contemplated life on the national stage. At the time, 20,000 copies were printed and the book seemed destined for the remainders stacks.

Mr. Obama’s confessions were not an issue during his Senate campaign two years ago. But now his open narrative of early, bad choices, including drug use starting in high school and ending in college, as well as his tortured search for racial identity, are sure to receive new scrutiny.

As a potential candidate, Mr. Obama has presented himself as a fresh voice offering a politics of hope. Many say he offers something new in American politics: an African American with a less-than-traditional name who has so far demonstrated broad appeal. What remains to be seen is whether the candor he offered in his early memoir will be greeted with a new-style acceptance by voters.

As a presidential candidate, President Clinton thought marijuana use could be enough of a liability in 1992 that he felt compelled to say he had not inhaled. And President Bush has managed to deflect endless gossip about his past by acknowledging that he had an “irresponsible” youth but offering no details.

Through his book, Mr. Obama has become the first potential presidential contender to confess to trying cocaine.