Obama will be fun to watch because he is going to crack up eventually. It’s inevitable. He just doesn’t have the experience to get through this thing. The press loves to build these guys up just watch them fall down for the sake of the drama.

For one thing, he said that as a youth he had inhaled.

“When I was a kid, I inhaled,” Mr. Obama said here to an audience of magazine editors. “That was the point.”

The direct admission was in contrast to Mr. Clinton’s denial in his 1992 campaign for president that he had smoked marijuana.

“I didn’t inhale,” Mr. Clinton said, cementing the idea that he liked to have things both ways.

Mr. Obama had written in his first book, “Dreams From My Father” (1995), before entering politics, that he had used marijuana and cocaine (“maybe a little blow”). He said he had not tried heroin because he did not like the pusher who was trying to sell it to him.

In an interview here on Monday conducted by David Remnick, editor of The New Yorker, at a meeting of the American Society of Magazine Editors, Mr. Obama said he was not making light of the subject.

“It was reflective of the struggles and confusion of a teenage boy,” he said. “Teenage boys are frequently confused.”

Since Mr. Clinton’s statement, the question of drug use has become a standard one for politicians, sometimes as a test of their ability to be straightforward. If the politician has used drugs, conventional wisdom says it is best to try to get the question out of the way early.