The buy email lists, is what it is. Example:
I still have an AOL account from when I was a teenager (just 'cuz). It was a sub-account of my dad’s account, and he made donations over the years to various Republican organizations, but never over the internet, always snail mail.
So, at some point AOL sold their subscriber list (honestly, probably from the start), listing the billing info of the person paying the bill for the sub-accounts. That list got bought by right-wing organizations, and now for years I’ve been getting Republican donation emails asking for money, sometimes addressed to my father.
The funny thing is that in recent years, it seems like the smaller-time politicians have been hedging their bets by not listing their party association and using what can only be described as “Democratic” color schemes, i.e. dark blues instead of bright reds. Sometimes, they have no party affiliation on their similarly themed site, and you have to find their association by checking Wikipedia. Very strange stuff.