When Barack Obama was an Illinois state senator running for the U.S. Senate in 2004, reporter David Mendell was baffled by the candidate’s “occasional unease with my presence.”

Mendell, who worked for the Chicago Tribune, knew the reason by the time he wrote the 2007 biography “Obama: From Promise to Power.”

“Obama was a secret smoker — and he did not want to light up a Marlboro in front of a reporter,” Mendell explained. He said Obama believed smoking would hurt his public image.

President Obama still smokes. He and his White House work hard to avoid the subject, and he has been trying to quit. But “there are times where I mess up,” he admitted in a news conference Tuesday. He proclaimed himself “95 percent cured” and said he never smokes in front of his two daughters.

The president’s continuing tobacco addiction added an element of “Do as I say, not as I do” to his signing last week of historic legislation allowing the Food and Drug Administration to regulate tobacco.

Logically, you might have thought the FDA had that authority long ago. After all, tobacco is a known health hazard, estimated to kill 443,000 Americans and cost $193 billion in lost productivity every year. The FDA is supposed to protect us from such hazards.

But the tobacco industry’s lobby is well-financed and slick. And tobacco is unlike other FDA-regulated products because they have health benefits as well as hazards. With tobacco, there is no good for the FDA to balance against the bad.

The FDA will now have authority to require changes in tobacco products, including limiting nicotine and flavoring. It can make ingredients public. It can consider harm to bystanders through secondhand smoke. It can restrict marketing and promotion. And selling tobacco to minors will be a federal offense.

The new FDA authority is long overdue, and it should help reduce smoking, especially among young people.

Another deterrent should be Obama’s example. Those who are thinking about starting to smoke should note that even this famously intelligent, disciplined and accomplished man got hooked and regretted it.