Okay, that makes sense. I'm in the UK and voting spam outside of obvious political groups like the EFF that you would have signed up to doesn't appear to exist.
Political activity was specifically excluded from our already sad and almost never enforced spam laws. Further, individual campaign donations are considered a matter of public record. So individual donors get recorded in these databases, and then private companies like NGP will harvest those databases, cross reference / deduplicate people with other databases, figure out their email and text contacts and then sell that information to candidates and parties who will in turn use it to spam you nonstop across email and SMS for every subsequent or similar election.
Good times.