The UK system gives both a minimum and a cap. Parties are entitled to a TV slot and I believe each candidate gets a free constituency mailshot as well. Beyond that the amount of money that can be spent is supposed to be capped.
I wonder how I would be able to spot the difference in practice?
It's better if people see all messages with proper attribution rather than an intermediary deciding what's allowed and what is not.
Incidentally, in the US at least, the old fashioned TV networks are require to offer all political candidates the same, lowest, media rates. PACs and outside money pay market rates.
We’re talking about targeted ads on social media.
When it’s whispers tailored to individuals playing on their hopes and fears…
It isn't in Europe. Most European countries have limits on how much can be spend on political campaigning and when campaigning takes place, and the difference between the smallest and largest parties is within the same order of magnitude, this is so because if one can simply buy an election this has nothing to do with democracy, an equal competition of ideas unrelated to one's financial resources.
Democracy isn't a contact sport, it's not even a sport, it's intentional deliberation between ordinary people at an appropriate place and time. Turning politics into 24/7 live TV bread and circus entertainment is exactly what's destroying it.