By now, you probably have heard the rumors about Barack Obama and drugs. A recent New York Times report suggests the leading candidate for the Democratic presidential nomination misled the public about his history of drug use -- by making it seem more impressive than it really was.

This is a welcome twist on the usual story of politicians' youthful experimentation with illegal intoxicants, which features evasions and false denials rather than forthrightness verging on exaggeration. But in the end the Illinois senator's narrative is disappointingly conventional, reinforcing the myths that underlie a drug policy he has rightly called "an utter failure."

In his 1995 memoir "Dreams From My Father" (written before he had run for anything but editor of the Harvard Law Review), Obama recalls smoking pot and snorting cocaine in high school and college; he says he even considered heroin before fear dissuaded him. "Junkie. Pothead," he writes. "That's where I'd been headed: the final, fatal role of the would-be black man."

Obama explains that he got high not "to prove what a down brother I was" but to "push questions of who I was out of my mind." In marijuana, he says, he "sought something that could flatten out the landscape of my heart, blur the edges of my memory."

Although Obama gives the impression that he had a serious problem with drugs, "more than three dozen friends, classmates and mentors" from his high school and college days who were interviewed by the Times remembered him as "grounded, motivated and poised, someone who did not appear to be grappling with any drug problems and seemed to dabble only with marijuana." A college friend said Obama "was not even close to being a party animal."

It's pretty damning stuff. But as the Times acknowledges, there are several possible explanations for the apparent inconsistency. Maybe Obama carefully concealed his drug problem, maybe his friends are trying to protect him by downplaying his drug use, or maybe Obama "added some writerly touches in his memoir to make the challenges he overcame seem more dramatic."

That last explanation seems most plausible, and it's too bad the writerly touches paint such a misleading picture, implying that occasional pot smokers are just a step removed from addiction and death. In public comments since writing the book, Obama has stuck to the narrative of sin and redemption, calling his drug use "bad decisions" that held him back.

Even so, Obama's comments have attracted criticism. Last fall, former Republican presidential candidate Mitt Romney said that "it's just not a good idea for people running for president of the United States who potentially could be the role model for a lot of people to talk about their personal failings while they were kids because it opens the doorway to other kids thinking, 'Well, I can do that too and become president of the United States.'"

The thing is, that happens to be demonstrably true. And until politicians admit that smoking marijuana, something at least half of American adults born after World War II have done, is not a harbinger of ruin but a generally harmless rite of passage, they will not be able to have an honest discussion about drug policy.

Obama has gone further than most. He has acknowledged his own pot smoking, and in 2004 he said "we need to decriminalize our marijuana laws," which in the United States usually means people are not subject to arrest for possessing small quantities of the drug.

What Obama has not done is connect the policy of not treating pot smokers as criminals (a position from which his campaign recently seemed to retreat) with his own experience as a pot smoker. Obama would not be better off today if he had been arrested for marijuana possession in high school or college, and there's no reason to think that experience would improve the life prospects of potential presidents who today are sneaking a puff here and there.