A problem for democracy
These new regulations could potentially pose a serious problem for democracy, especially local democracy. At present political parties can collect and use e-mail addresses with a relatively simple disclaimer on a form, and provided all the expected unsubscribe options are offered. After GDPR it is likely that explicit permission would be needed for every separate use of an e-mail address.
The upshot of this is that it would become far harder for political parties to communicate directly with the public and instead news organisations would effectively become the only source of information. The problem of editors distorting or ignoring anything they don't like is obvious. Local politics would suffer most as it is rarely deemed that newsworthy anyway.