Ok, so I spoke with our attorney about this. I'm really glad you brought this up so we could be clear in the answer here.
Quantity discounts, artwork "easiness" discounts/extra "PITA" charges, loyal customer discounts, price matches, first time customer discounts, first time customer extra artwork fees, etc are all just fine to charge or discount to a politician -
as long as you would normally offer these same discounts or additional fees throughout your normal operation of business.
Selecting a particular politician or political party and offering a discount to "All Democrats" or "All Republican Candidates that will lower taxes in Pawnee County" is crossing a line into a political contribution.
Basically, you should be safe as long as you treat them all fair, like any other paying customer.
***Please note I am not an attorney and don't know the laws in your state or country, so don't take my advice at all.
