As far as I'm aware its not a "rule" but a law, hence the ability to punish those who break the law - and yes, it has been about for years, but not as far back as Ataturk. He would never sign of on something like that, he liked the raki too much!
Its the YSK (the election board) who stipulate when and how long the ban is for - I think it ends up in the official gazette to make it a "law".
I'm fairly sure that the ban ended at 6pm in Istanbul last general election and I seem to remember one election (a good few years ago) where the bars in the Paspatur were all closed during the day but opened at 6 or 8pm and from then on it was business as usual.
Don't know what all the fuss is about, I mean its one day every two or three years. If someone is so desperate for a drink that its an issue, then they've got bigger problems to think about.
JF