One way to protect yourself — and I’m going to do this in the future — is to open up a separate bank account at a separate bank (from all your other accounts) and get a debit card (with no credit) and keep the account balance very low, close to zero.
When you want to donate $500 to someone, transfer the $500 from one of your “real” accounts and use the debit card to give that $500 to the candidate of your choice.
For a little effort (it’s easy), you not only protect yourself but you have the satisfaction of thwarting potential political attacks on your money.
I have a feeling that this is going to be unpopular, but another way to protect yourself is to use Bank of America's "Shop Safe." I honestly have no idea if any other banks have a feature like this, but the other banks with whom I do business do not.
"Shop Safe" allows you to set up "pseudo-cards," with a unique card number, expiration date (you can set it up to expire in as little as 2 months), and a maximum spending limit (which can be increased or decreased as needed), and that 3 digit security code. While the charges are charged to your "real" BofA credit card, none of the account information of your "real" card is released. Another bonus is that once you've used that card number at one vendor or merchant, that account information is ONLY valid for that vendor or merchant - nobody else.
I use it all the time when I do on-line purchases, and I've been using for about 3 years now with no problems at all. Another place where it's very useful is for "subscription services" that can sometimes be a nightmare in canceling. You can set up the "card" to expire whenever you like, so the company can't keep charging you after you've told them to stop. In the past, I've had to contact the credit card company to have the card canceled and get a new card issued, which was a hassle.
Like I said before, I know that Bank of America isn't terribly popular here, but this is a feature that works well, and I haven't found it at any other bank with whom I do business.
Mark
A better option is to use PayPal when possible or to get temporary credit card numbers, which can be offered by the bank through which you have your card. These can be generated online.