What you need to truly defeat this sort of spam is personalization, AKA recommendation,
If the top news stories are personalized to your interests, it is more difficult to game the system.
In particular, consider this scenario: I get a news result from a voting ring, and it ranks high because they all voted. But then I downvote the article because it is not interesting to me, Afterwards, the voting ring's weight is diminished in my personalized news feed. Hence, they cannot artificially rank articles for you,
I would argue that without some personalization, it is impossible to 100% avoid spam. Because if you treat there as being one objective lense, it is hard to discriminate between legitimate overlapping interests and colluders who share their authority.