Judging from recent history, any young person who aspires to be president should be aware that certain attributes seem to be critical. You have to be male. You have to have an Ivy League degree. You have to have been a governor or senator. And, don't forget, you have to have smoked marijuana.

That is something all the presidents in the past 20 years have in common. Bill Clinton admitted it, while claiming he didn't inhale. George W. Bush refused to deny getting stoned, saying, "When I was young and irresponsible, I was young and irresponsible."

Barack Obama said, "When I was a kid, I inhaled. That was the point." Presumably, Mitt Romney never did, and who knows? Maybe he'd be ahead in the polls if he had—though, he might note, it's never too late.

Logicians will quarrel with my reasoning, arguing that drug use did not propel these men to high office. That's true. But it obviously didn't hinder them.

For decades, champions of the drug war have trumpeted the dire risks of marijuana. But millions of Americans have used and even enjoyed it—nearly 100 million, in fact. Most of them have gone on to lead responsible, well-adjusted lives.

If anything related to pot would have kept them from being elected to office, it would be the laws against it. An arrest or a conviction could derail a political career before it even got started. Yet these presidents went on putting people in jail for something they got away with.

Their fellow citizens, however, are increasingly skeptical about the drug war. Last year, Gallup found that 50 percent of Americans now favor legalizing cannabis, with only 46 percent opposed.

The sentiment may lead to action. On Nov. 6, residents of Colorado, Oregon and Washington will vote on ballot measures to allow the regulated production, sale, and use of pot.

In Colorado, which already has a large network of medical marijuana dispensaries, familiarity has bred acceptance. One of the most noteworthy headlines of 2011 came on a news release from Public Policy Polling: "Colorado favors gay marriage, marijuana use, loves Tebow." Affection for the Denver quarterback may have ebbed since he went to the New York Jets, but the Regulate Marijuana Like Alcohol Act of 2012 is leading in the polls.

Weed would remain illegal under federal law, but good luck to the feds trying to enforce that ban if a state abandons it. As the Drug Policy Alliance notes, medical marijuana has gotten established over the objections of Washington.

Critics raise the usual alarms. Obama's Office of National Drug Control Policy charges that "political campaigns to legalize all marijuana use perpetuate the false notion that marijuana is harmless. This significantly diminishes efforts to keep our young people drug free and hampers the struggle of those recovering from addiction."

But very few people portray marijuana as harmless. The claim, grounded in fact and experience, is that it is far less harmful than the effort to stamp it out.

Marijuana prohibition means the arrest of some 750,000 people every year for simple possession—double the number 20 years ago. It means spending an estimated $7.7 billion on enforcement. It means the enrichment of urban gangs and Mexican drug cartels that depend on the illegal trade. And the whole effort has been a complete failure.

Nor does a permissive approach necessarily undermine efforts to protect kids. For high school kids, dope is just slightly harder to get than Skittles. In the Netherlands, which permits regulated sales through "coffee shops," adolescents are far less likely to try pot than here.

Marijuana use, it's true, can be damaging. A recent study found that people who begin using it heavily as teens and continue as adults can reduce their IQ. It can cause dependency. Like any mind-altering substance, it may foster dangerous behavior.

But the same things are true of alcohol, a drug that inflicts far more damage to users and the rest of us than marijuana could ever do. We accept those risks as the price of personal freedom—while focusing law enforcement on combating abuse, not use. A similar respect for individual prerogative ought to govern in the realm of cannabis.

Young people should realize that, despite the example of Obama and his predecessors, smoking pot doesn't mean you'll grow up to be president. But be warned: It is one of the risks you take.