Political parties are not optimising for fair. They want to preserve the advantage rich and powerful parties currently enjoy.

This is why when people say they don't take money from big corporations or rich donors, it's such an important factor. It's not just that you as a political party are incentivized to what they want so they will keep giving you money. Even if you donÄt directly succumb to their demands, you are incentivized to keep them rich so they will keep having all that money to give you.

No, but the political party that wants to ban advertising will have a hard time finding an advertising agency.

They could just carve out an exception for themselves