I've been trying to figure this out for 2 weeks and, from what I can tell, it seems that the amount of people who vote on a poll doesn't affect how much gold is produced due to that one poll. The amount of gold you earn upon a poll's immediate creation (as soon as you hit "publish") is all you'll ever make from that poll.
However, it seems that the number of people who vote in a poll affects how much gold follow-up polls produce. If it's your first time making a poll in a spot, you'll probably only earn somewhere between 1 and 20 gold for that poll. Then, if the poll has at least 3 people vote in it and I wait 24 hours to make a 2nd poll, I'll earn between 200 and 400 gold on that 2nd poll (even in a spot I have no medal in). However, if I go on a poll-making spree and create 10 new polls within an hour, I'll earn 200 gold on the first poll and only earn 1 gold per poll on the other 9 (even if the other 9 are on a different spot than the first one). So it appears that if you make quality polls and spread them out over time (only making one a day), that's how you earn the most gold. Obviously this is a complicated system and there's more to it than I can figure out, but these have been my observations thus far.
