I can't speak for the rest of the nation, but that map is highly accurate for the South. And no, it doesn't really draw a parallel with the election results, as 'coke' is probably used 95% of the time even in urban hubs. Ask for a soda and you'll get some off-brand crap out of a 2-liter bottle; ask for pop and you'll get a pop from a fist (I am not kidding; unless you have a Northern accent perhaps, then they will just run you out of the state).
Here's how a convo would go around here:
Person 1: "Can I have a coke?"
Person 2: "We're out of coke."
Person 1: "D'ya have a dew?"
Person 2: "Yeah sure."
*gets a Mountain Dew*
If you say 'coke', you'll normally get Coca-Cola because that would be what you want, unless the home has Pepsi, then you'll get Pepsi. If you want Pepsi, you say Pepsi. 'Dew'/Mountain Dew will get you a Mountain Dew. Sprite will get you a Sprite. 7-Up will get you a 7-Up. We're actually pretty specific about asking for what we want when compared to other regions. Terms like 'pop' and 'soda' sound so general; we say what we want.