One of the blessings of having a loved one in politics is that I know who is/isn't selling their lists. There's only a small handful of organizations who adhere to a firm "no list buying, no list selling" policy. Whoever you donated to apparently has dreadful data ethics. Once your number is in a major political/nonprofit consultancy's database, they'll happily hand it out to all of their other clients. You have to trust that the campaign you support isn't going to give them that data... which is, of course, impossible to know from the outside.