Debates and actually adressing the problems.
You can’t say “Party X just wants your money”, try “Our party will help you keep your money”, or even “Unlike some parties today, we will put your taxes to good use”.
It’s a lot harder to make a compelling attack without a concrete focus. “Some parties are corrupt” is so trivially true that’s it embarassing, but “Party X is corrupt” is a rallying cry.
It won’t prevent lies by any means, but since specific claims can only be nade about your own party it gives an advantage to talking about your own party instead of every ad being incredibly negative claims one step off of a flame war. Hopefully that leads to building a strong case and then defending that case during debates, but at least the ads will have less direct negativity.
It would be more positive, but potentially less accurate. A party that does a lot of very specific and bad stuff but has some vaguely good policies to point towards would beat a neutral party, even if they shouldn’t.
Maybe if you only see the political ads of a single party. It would still be better because you would know of even a single stance of one party.
Last election, I can’t remember a single actual stance taken by any party based on political ads. They were all attack ads. Without discussion you couldn’t separate the resonable accusations from the trash anyway.
Basing your politocal opinions purely on ads is a terrible stance anyway, and the party best at fearmongering will win there. There aren’t any restrictions on ads that can fix people forming opinions only on ads anyway, we’d need to encourage public political debates and discourse instead.
