The same places that non-political telemarketers do. Many retailers sell customer info, as do credit bureaus/financial services organizations and telecom firms.

The same places that non-political telemarketers do. Many retailers sell customer info, as do credit bureaus/financial services organizations and telecom firms. Google “phone data appending” and you’ll find lots of data brokers. I run a free site at https://simpleoptout.com https://simpleoptout.com that makes it easier to opt-out of data sharing. Doing that is the first step, but suitably motivated buyers (which includes the national parties) will still find someone selling your data. One other step helps: when there’s no need for an entity to have your phone number, don’t provide it. If a phone number is required for no reason, provide a fake number at an area code that’s not in use. This can easily reduce the privacy “attack surface” by 50%. Every random e-commerce vendor does not need your phone number to fulfill your order.