On Monday at a forum in Miami, Sen. Marco Rubio of Florida, a likely Republican presidential candidate, was asked about legalizing marijuana. Here’s what he said:

Question: You’ve said that you don’t think legalizing marijuana or even decriminalizing it is the right decision for our country. … Young voters have asked me, and they’re curious to know: Have you ever smoked marijuana?

Rubio: You know why I never answer that question? I’ll tell you why I never answer that question. If I tell you that I haven’t, you won’t believe me. And if I tell you that I did, then kids will look up to me and say, “Well, I can smoke marijuana, ‘cause look how he made it. He did all right, so I guess I can do it, too.” And the bottom line is that it is a substance that alters your mind. Now, when I was 17 and 18 and 16, I made dumb decisions as is. I didn’t need the help of marijuana or alcohol to further that. … And I know I’m sounding like a 42-year-old dad, but … Here’s the problem: You can make mistakes at 17 that will be with you the rest of your life, OK? When you go interview for that job, and that thing pops up in your background check, that you got arrested for something dumb, they don’t look at you and say, “Ah, you were just 17.” There are people that won’t get hired because of that stuff. … And that’s the problem with that question. So the answer to your question is, at this point, it’s irrelevant.

The first thing to notice about Rubio’s answer is that it’s circular. The issue presented to him is whether marijuana should be legal. Rubio replies that you shouldn’t use pot because it’s illegal. That’s an assertion disguised as an argument.

He invokes this circular argument to justify his evasion of the question. The question has an obvious moral and policy basis: Young people want to know whether Rubio thinks it should be against the law for them to do what he did. His response is that he won’t answer that question, because saying you smoked pot sets a bad example for kids.

This is the same argument George W. Bush used when he was running for president. In recorded conversations with an adviser, Bush said his “strategy” was to refuse to answer questions about his drug use. "Do you want your little kid to say, 'Hey Daddy, President Bush tried marijuana; I think I will’?” Bush asked. He concluded: “I wouldn't answer the marijuana question. You know why? Because I don't want some little kid doing what I tried.”

The notion that you’re ducking the question to protect children, rather than to hide your hypocrisy, is wonderfully convenient. But the Drug Enforcement Administration, which enforces the laws you’re defending, says you’re wrong. Sixteen months ago, the DEA, in conjunction with the U.S. Department of Education, issued an advice manual titled, Growing Up Drug Free: A Parent’s Guide to Prevention. Here’s what the manual says:

At some point, your child is likely to ask, “Have you ever used drugs?” Do not be uncomfortable with the question. Instead, be honest and use the opportunity to talk with your child about the importance of avoiding drug use. If your answer is NO, explain to your child how you were able to avoid temptation and peer pressure, the reasons you felt it was important, and why you are happy that you chose to do so. …

If your answer is YES, expand on that with why you don’t want your child to do the same thing. You don’t need to confess every single event from your past. Skip the details and explain honestly what attracted you to drugs, what you’ve since learned about the dangers of drugs, and why you want your child to avoid making the same mistake.

That’s good advice. When you tell a child that it’s bad or unwise to do something, and the child asks you whether you’ve done it, the most important thing isn’t to persuade the child that you’re clean. The most important thing is to tell the truth.

Marijuana, alcohol, and cocaine are just drugs. They’re the topic at hand. It’s natural, as a parent, to assume that what you’re teaching your child about is the topic at hand. In reality, the child is absorbing what’s going on beneath the surface. What’s going on beneath the surface, in a conversation about your foolish, dangerous, or immoral behavior, is an examination of your candor. What the child wants to know most of all isn’t whether you ever did drugs. It’s whether this conversation is for show or for real.

Kids aren’t stupid. When they ask whether you’ve smoked pot, and you evade the question, they don’t conclude that it’s bad to smoke pot. They conclude that you think it’s OK to hide the truth from your kids. What they’re learning from you is deceit. The best thing they could do, in terms of character development, would be to reject your example, not follow it.

The same is true, less directly, of politicians. When a senator says it’s bad to smoke pot, and young people ask him whether he’s ever done it, and he says he won’t answer the question because it might set a bad example, he’s already setting a bad example. He’s teaching them that politicians are cagey and self-serving. Or, worse, he’s giving them the idea that it’s OK to dissemble this way with your own kids.

The better model is former Sen. Rick Santorum of Pennsylvania. Two and a half years ago, when he was running for president, Santorum took this question from Piers Morgan:

Question: Have you ever broken the law, senator?

Santorum: Well, yeah. I admitted, back when I was running for the Senate, that when I was in college, that I smoked pot, and that that was something that I did when I was in college. It was something that I’m not proud of, but I did. And [I] said it was something that I wish I hadn't done. But I did, and I admitted it. And I would encourage people not to do so. It was not all it's bound up to be. 

Some young people who saw that interview probably concluded that Santorum, having smoked pot, had no business telling anyone else not to touch it. But others may have been moved by his sincerity. Santorum wasn’t modeling drug abuse. He was modeling honesty. He was opening other people’s hearts by opening his own.

You should try it, Sen. Rubio. It’s pretty great.