Okay, yes, this is real, but let me explain. Al Smith was one of the lesser-known Presidential candidates, running against Herbert Hoover in 1928. Smith was a "wet" candidate which simply meant that he opposed prohibition which was still in effect at the time. Hense, "make your wet dreams come true". And yes, I have verified that at the time the expression held the same meaning it does now- a bit of a flop on the part of Smith's advisors. 

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Although now hailed as perhaps the worst campaign slogan ever, I have to argue that his opponent's wasn't much better. Herbert Hoover campaigned under, "A Chicken in Every Pot and a Car in Every Garage" - seems like he's alienating vegetarians and bike fans, but what do I know.