Add a new Dynastic Rule to the Ruleset.  Call it “The Coup” and give it the following text:

If at any time there are at least three Insiders, and one Insider is supported by every other Insider, the supported Insider achieves victory.  Achieving victory in this manner is called “winning by consensus”
If at any time there is exactly one Insider, that Insider achieves victory.  Achieving victory in this manner is called “winning by default”.
If at any time there are no Insiders, all Outsiders immediately become Insiders. This is called a Coup.