So, what do you think? If you see a business that has a poster for a candidate that you are opposed to, does it cause you to go to another store or do you just go in and shop anyway? What if it is a candidate you favor? Do you buy more? Would you go to a new store because they support your candidate?

Ideally, we should be able to treat our fellow citizens the same no matter which candidate they favor. But when the political divide gets wider and wider, and rhetoric gets hotter and hotter, I can't help but wonder whether the money I would spend in the store might not end up supporting candidates I oppose.
Would it be better if they left the sign off? Then they still might use my payments to support candidates I oppose, but I wouldn't know. (Well I could look at the
APOC reports.) Does posting a sign on your business constitute an in-kind donation? What if Conoco-Phillips put a huge banner down the side of their building?
I remember once asking the owner of an ethnic restaurant about the large poster of a candidate in the window. "The candidate eats here often and asked to put it up. We couldn't say no." Notice how skillfully the owner did not tell me if they supported the candidate or not.
Do such posters help a candidate? Do yard signs help a candidate? I would gess they do help persuade the undecideds. If you see lots of signs, especially if you know and respect the people whose yards they are in, you get a feeling that this person has widespread support. Especially if you want to fit in, be like everyone else. But some people may be turned off by the signs, especially if they are put up illegally.* (See below) I tried finding some articles on this, but didn't come up with anything recent. I guess people just assume it works.
For people who feel strongly against a candidate, seeing that candidate's poster in the window of a store they are about to enter, surely has to cause them to pause. Do you tell the owner why or just leave quietly?
The owner has the right to express his or her opinion. Is not shopping at a store that posts a sign for the candidate you dislike a political boycott? I think that going seeking the information about which candidates which business owners support and then telling people to avoid those businesses moves more into the boycott territory. Customers have a right to shop there or not. Business owners can support candidates many ways. If they want to post signs at their business, they have to consider the possible impact on their business.
But I do think the restaurant owner I mentioned above could have declined, saying that they didn't want to offend potential customers by having any political signs. They could then offer to have a sign at their house if they did support the candidate. Or, conversely, they could also allow the opponent to post a sign, though the opponent would probably assume they support the other candidate and wouldn't ask.
*While trying to get some information for this post I did find this about putting signs on roadways from the
Department of Transportation and Public Facilities:1. Campaign signs placed within the State’s road and highway rights-of-way are deemed unauthorized encroachments under AS 19.25.200 – 19.25.250 and will be removed by DOT crews without notification. Vehicles parked in rights-of-way that are used to display political advertisements are also prohibited and subject to removal. Political campaign signs are considered outdoor advertising. 2. AS 19.25.105(a) states, “Outdoor advertising may not be erected or maintained within 660 feet of the nearest edge of the right-of-way…” This section deals with advertising outside the corridor, but also addresses advertising that maybe placed within the corridor on bus benches or trash receptacles. If the sign is on private property, DOT must provide a 30-day written notice of removal to the sign owner and property owner.