Even if you don't mind paying full price (since it is a donation to the campaign), I would suggest using the discount to buy a few extra things you wouldn't normally buy that would be easy to hand out to others or give to like-minded friends (like some bumper stickers or pins).

You may want to think about getting one of the Pride shirts/hats because I feel like that would especially trigger a lot of libs:

https://shop.donaldjtrump.com/products/trump-pride-2020-ringer-tee

https://shop.donaldjtrump.com/products/make-america-great-again-2020-price-hat