@NiveusLepus I think it's tribal in the same way that people wear sports merch. Solidarity with other people who support the same team. In the same way that a Lakers fan doesn't see a Bulls hat and switch teams, I don't think political merch does anything to change minds either. It's about identity.
It's also curiously American.
I've *never* seen a Brit on the street wearing a hat saying "I vote Tory" or "Labour 2024". Even campaign staff.