5. Arguments presented by external sources must include data if it is not already known to you.
"Vote for Smith!" is an extremely poor argument, because it doesn't even qualify as one at all! It is missing a supporting premise. "Vote for Smith because she'll reduce crime!" is a better one, though it carries many heavy assumptions including that Smith has promised to follow a certain course of action once in office, and that that course of action will have an effect on reducing crime. So it's still not of much use, although this tagline may prompt you to go look at Smith's website. There you can read her expanded platform which describes the policies which she believes will cause a reduction in crime.
This is the type of complex issue where assumptions carry a huge amount of weight. Smith's website may state that her crime-reducing policies include a 10pm curfew for teenagers, as teenagers are the cause of much crime. Smith's site may not expand any further; and though this provides some useful data, there are still many assumptions here. Some people may be convinced at this point, because they already know the assumped data. They have researched the matter in the past and believe that teenagers are the cause of a lot of crime and that teen curfews in other cities have been effective at lowering crime rates. Thus, if you don't already have this data, it will be up to you to track down the supporting data to confirm or negate her claim.
Even if you confirm that piece of information, the higher-level conclusion - that you should vote for her - is still pending your conclusion that reducing crime is an important priority for the city, moreso than any issues being prioritized by other candidates.
You may think that not including assumed data is always a bad idea, but in fact it is very necessary for anyone to ever be able to communicate. Smith's argument also assumes that you think crime is undesirable and would prefer if it were lower. But it would be pointless for her to rattle on about the negative effect that theft can have on someone's property or assault can have on someone's health. It is very reasonable to assume that most votes are interested in minimizing crime. Even the definition of crime could be debated: does it include just violent crime? any felony? any violation of the law, including a speeding ticket? Does it include any sort of ethical violation, no matter how minor, such as verbal insults? But for her to spend a lot of time describing what she considers crime would be wasteful of space, as most people are in agreement that crime refers to the basics of theft, fraud, and violence, and more broadly anything classified as criminal by the city's existing legal code. Assumptions are wholly necessary and good; just make sure that the assumptions hidden within an argument match up with your pre-existing data.