One thing is for certain during election campaigns, people are more likely to share their opinions across the counter. This is especially true of newspaper shoppers making their purchase and commenting on election related stores they notice on the front page.
While most comments are harmless, there are some delivered with venom, hate even, that require effort to listen to without commenting back.
One way to diffuse the situation could be to have a politics free zone established and extract a ‘fine’ for people who do comment. Have two or three charity tins for people to donate a coin as a ‘fine’ for them commenting. the charities you collect for could be those of prominent local candidates – the donations are a way of voting.