After struggling to quit smoking in the past, Sen. Barack Obama is trying a cessation aid not available over the counter: public attention. Obama (D-Ill.) resolved to quit his cigarette habit over the winter holidays, just weeks before his expected presidential campaign would make photographers and reporters an even more regular part of his life. He said in a Monday interview that, although he has never been a heavy smoker, he has quit for periods over the last several years but then slipped back into the habit. On the cusp of a potential presidential bid seemed the right time to...