Who would have figured it...Mac Daddy McCain likes to throw the bones (from a May, 2005 profile of John McCain in The New Yorker by Connie Bruck):

McCain is an avid gambler. Wes Gullett, a close friend who worked for McCain for years, told me that they used to play craps in Las Vegas in fourteen-hour stints, standing at the tables from 10 a.m. to midnight. “Craps is addictive,” McCain remarked, and he headed for the fifteen-dollar-minimum-bet tables.

Fifteen dollars might not seem like a lot, but most serious players place odds bets and take advantage of other wagering opportunities, easily placing hundreds of dollars on the table per roll.

Here's a camera phone picture of John McCain (or someone who looks exactly like him) throwing dice in Las Vegas. Even though the site I found it on says it was taken at Mirage, I'm pretty sure McCain is actually at Bellagio in the dice pit closest to the main tower elevators. (I think that's the Fontana Lounge in the upper right hand corner of the picture, and it is apparently daytime.)

I think the picture is from summer 2006

A Las Vegan, I'm glad that he likes to play -- I don't think there's anything wrong with it at all. I do wonder what his "traditional values" political base would think, though. Maybe he and Bill Bennett went on junkets together?

Here's the full excerpt of the story about McCain playing craps from The New Yorker.

Many of McCain’s friends comment that he is far more serious and focussed than he has ever been, and that they rarely see the McCain they knew—irrepressible, occasionally outrageous, impolitic.

But that character is not altogether obsolete. The moment the car stopped at McCain’s hotel in downtown New Orleans, he set out at his usual fast clip for Harrah’s, across the street. McCain is an avid gambler. Wes Gullett, a close friend who worked for McCain for years, told me that they used to play craps in Las Vegas in fourteen-hour stints, standing at the tables from 10 a.m. to midnight. “Craps is addictive,” McCain remarked, and he headed for the fifteen-dollar-minimum-bet tables. At the most obvious level, the game is incredibly simple—players rotate turns throwing the dice, and you either win or lose depending on what number comes up. But McCain’s betting formula makes it much more complicated. “Uh-oh!” he cried, as a player accidentally threw the dice off the table. “This is a very, very superstitious game,” he said. When his turn came to throw the dice, he picked them up and blew on them first. He had placed chips on the number 5, so (envisioning a combination of 2 and 3) he called, “Michael Jordan! Michael Jordan!” A few minutes before, McCain had tried to move closer to the table and another player refused to make room. Now, suddenly, the man swung around, peered at McCain, and exclaimed, “I just realized who you are! Here, take my place.” When McCain demurred, the man went on, “No, you’ve gotta take it! I admire you so much! I wish you all the luck next time!” As he walked off into the crowd, he muttered, “I just wish you’d run the last time, instead of that other guy.” 

Note that whatever betting "system" Mac Daddy McCain is using is proof that he's a sucker -- there's no system (at least no legal system) that gives you an edge on the dice tables in Vegas.