I had an idea after i posted - maybe we could allow between-campaign advertising, but deduct the costs of those ads from the party's overall campaign limit for an actual campaign. That would at least force parties to decide if they really wanted to bother with attack ads during a non-election period.

As for 3rd parties - are there a lot of groups that do this? And do they do it between elections? I've been trying to think of any examples and the only one that comes to mind is the NCC - i recall they'd really gone after the Liberals a couple of elections ago, but i think that was only during the actual election campaign. I can see an interest group taking out ads to campaign against a government policy initiative between election campaigns - but to me that's targetting the policy moreso than the party specifically. They might not have any other issue with the party in power, just that one issue.