MANY guys continue to smoke after they get married no matter how much they love their wives. This is reality, and if you are willing to risk your life by dating a smoker, please do NOT have any illusions that he (or she) will likely quit. Is it possible? Yes, and I do know one or two people who have. But are the odds in your favor? NO WAY!
You can ask your mechaneches, Rav or whomever you look to for advice, but there is no person on this planet, no matter how many other maalos they have, that is worthwhile dating if he is so lacking in middos and brains that he is a smoker, even a “once-in-a-while” smoker. It’s very wrong and it speaks terribly of the person who smokes.
I happened to have been at a popular minyan factory in a certain well-established frum neighborhood and it was disgusting that there was no smoke-free area of the shul that I could get to and (not that anyone was smoking in shul, but) the strong lingering stench of cigarettes was repulsive (and a chilul Hashem). We are an am navon vichacham and yet this is what a shul smells like!?!
Also, anyone who starts to smoke now has an even lesser likelihood of quitting than someone who started 10 years ago, as someone who starts now is ignoring the many additional years of further medical knowledge of this deadly disgusting disease-causing dumb and deranged ADDICTIVE habit.