Well, Obama would hardly be the first smoking President. FDR wouldn't allow himself to be photographed in his wheelchair or on crutches, but in most of his photos, we see him with that trademark cigarette holder clamped in his jaws.

I can't think of any such blatant tobacco use among more recent Presidents. JFK would occasionally be seen smoking a cigar, and then there's Bll Clinton's other (alleged) use of cigars. Some of the other post-WWII chief execs may have been off-camera smokers, but I can't remember any of them appearing in public sucking on a cigarette.

Earlier than FDR, smoking was pretty common and completely uncontroversial, and I'm sure quite a few Presidents indulged without it ever being an issue.