WASHINGTON -- Barack Obama is trying to get rid of a bad habit. His wife, Michelle, has put out the word: Anyone who catches the senator from Illinois lighting up a cigarette should let her know, so he can catch hell from the missus.
It's with this blend of seriousness and playfulness that the Obama campaign is portraying the senator's efforts to give up tobacco. The campaign knows that a president who lights up like Humphrey Bogart is a nonstarter. But Obama's team also seems to be hoping that by framing his smoking habit as a matter of friction with his wife (who, of course, is only thinking of his health), they can take the edge off it as a campaign issue.
Maybe it will work. If Obama can stay off cigarettes until the primaries, his longtime smoking habit won't be an issue. But if voters start to smell tobacco on his suits, it could become a problem very quickly.
Smoking currently occupies an odd place in the pantheon of misconduct. It's not illegal, and millions of Americans continue to light up. Smokers can reasonably claim that their habits are their own business. But people whose lives are endangered by secondhand smoke -- like bartenders and wait staff -- tend to feel differently.
And then there's the example for children: The US government has gone so far as to ban many forms of cigarette advertising in order to prevent children from starting to smoke. Activists are trying to get Hollywood to ban smoking in all movies that can be seen by children without their parents' approval.
There seems to be a strong link between what children see and what children do: The activists targeting the movie studios point to a study in the medical journal The Lancet that found that watching people smoke on screen made children more likely to light up themselves.
Watching a president smoke, even if his wife disapproves, could easily make children believe that smoking won't hurt them.
They'd be wrong -- very wrong. Even after years of public service announcements, the public doesn't seem to understand the extent of the public health crisis. Smoking is a cause of heart disease and emphysema, and of many forms of cancer beyond lung cancer.
But the lung cancer statistics are the most striking: It is by far the leading killer among cancers, and 90 percent of lung cancers in men, and 80 percent in women, are attributed to smoking.
The federal government pumps tens of billions of dollars a year into the fight against cancer, and the news media follow every mini-advancement. But arguably every achievement put together, since the start of the "war on cancer" in the '70s, wouldn't equal the benefit of getting everyone to quit tobacco.
Put another way, the number of cancer deaths that would be prevented if everyone stopped smoking would be the equivalent of curing every single case of colon cancer, breast cancer, and prostate cancer combined.
As it happens, new treatments and early detection have led to significant progress in fighting those cancers -- the three most common other than lung cancer. Sadly, there hasn't been as much progress in treating lung cancer: About 90 percent of people who get it will die from it, usually very quickly.
Presidential politics has been a showcase for progress in cancer treatment. Betty Ford and Nancy Reagan were treated for breast cancer in the White House, and survived. Ronald Reagan had colon cancer, and survived. Three prostate cancer survivors -- Bob Dole, John Kerry, and Rudolph Giuliani -- have run for president in recent years. This year Giuliani is neck-and-neck at the top of the GOP polls with another cancer survivor, John McCain, who has had two bouts with melanoma, the most serious skin cancer.
There hasn't been a lung cancer survivor among presidential candidates, perhaps because so few people survive it. And it can't be comforting to Obama to know that as a man who smokes, he's 23 times more likely to get lung cancer than a man who doesn't smoke.
Obama recently drew headlines when he described the more than 3,000 Americans killed in Iraq since 2003 as wasted lives. (He subsequently apologized.) But he should know that about 600,000 Americans have died of lung cancer during the four years of the Iraq war -- almost all of them because of smoking.
He has many reasons to hope that Michelle doesn't catch him sneaking a quick drag before any tough debates.
Peter S. Canellos is the Globe's Washington bureau chief. National Perspective is his weekly analysis of events in the capital and beyond.