I used to try to evaluate all such appeals carefully and have contributed to many of them, but contributing seems quickly to proliferate in further appeals, not only from the organizations that have received contributions, but also from others who somehow obtain access to their mailing lists. Which leads to the subject of mailing lists. Each group has its own mailing list, but many of them frequently also lend or sell their mailing lists to other groups. The idea is that the wider the grazing area and the more often one grazes, the more one takes in. Incidentally, this type of fund raising is not confined to conservative political causes and fundamentalist Christian organizations.
Liberals do the same thing.
I also receive frequent donation requests from the American Humanist Association and various other anti-creationist and liberal organizations. I was rather surprised, however, to receive recently a fund appeal letter from that most prestigious of all scientific organizations, the National Academy of Sciences. At least that is what their letter claims, and it is probably right. It is a very prestigious organization and gets a great deal of its financial support from the government. Nevertheless, they need more.