Worlds Without Number: the faction rules can be used to model more than just political settings (and are based on the original faction rules in Stars Without Number). And both sets of faction rules are included in the free versions of the WWN & SWN rules.

I'm going to just say that I have yet to find a game system that handles politics better than a basic NPC flowchart using a pen and a blank piece of paper.

Pick a party (individual or faction; a PC or PC faction is a good starting choice), put them in the center and put two things under it... what they have, and what they want. Then put more parties down around them with what they have and what they want.

Next draw lines between the parties based on whether there is something one has or wants that the other has or wants... including if they both have or want the same thing (and whether the thing they both want is mutually exclusive; i.e. both want stability is cooperative, both want the throne is mutually exclusive). Note this on the line between them.

Continue out as far as you wish. This is your web of alliances and opponents at the start of your campaign and how the PCs uncover what others have and/or want and how they work to achieve or thwart those (thus making new allies and enemies) is your campaign's roadmap.

All the dice rolling mechanics in the world won't do as good a job at producing realistic results as just applying common sense to your flow chart; when the PCs help one party get what they want, they'll be more well disposed to the PCs, when what the PCs are doing gets in the way of what they want, they'll work to end the PC's interference.

Maybe throw some random events; droughts, famines, pestilence, accidents, migrations, etc.; into the mix if you're wanting an extra dash of unpredictability. Roll up a few in advance if you as the GM want to include portents or link them into cause and effect (ex. a famine leads to a mass migration with minor incursions in the months prior to the main wave's arrival).

Regardless, this amount of setup is almost always less than that needed for actual "domain level" rules while producing results that from the players' perspectives are just as good and generally more immersive (there's no "rulership" check to be made, the PCs have to decide their course of action as their characters and the GM just judges results accordingly.

Quote from: swzl on July 04, 2022, 08:15:28 AM
ACKs is currently my favorite domain/political set of rules. Axiom #3 coves this from the empire level down to how profitable is your small peasant holding.

+1

There is a guy on the ACKS discord who's working at hammering ACKS into place to handle Birthright, and I wish him well in the endeavor, though it is one I would never seriously attempt myself 

Pendragon? I'm not super familiar with the system, but I know it has stats for things like honor, glory and prestige. You'd probably have to hack it quite a bit to change the tone from Arthurian Romance to grimdark political drama though.

I believe Reign is the first RPG to provide detailed mechanics for running organizations, so that's a pro.

L5R is all about playing members of the ruling samurai clans, and there have been expansions that allow for larger scope play to be mechanically supported.

This new supplement for 5E 'might' be of interest to you.

Claims to turn 5E into a 4X (Explore, Expand, Exploit, Exterminate) game. I've not bought it but it does look interesting.

Castles & Crowns
https://www.dmsguild.com/product/406426/Crowns--Castles?src=hottest_in_dmg&filters=45469