Sprawling space 4x Stellaris' new expansion, Federations, lets you form a galactic community. It's an organization that spans the galaxy, and everyone is effectively a member whether they like it or not. (Except if you're space North Korea, or an empire of machine exterminators or what have you.) Anyways, the end result is basically the galactic senate chamber from the Star Wars prequel movies mixed with the real-world United Nations - various measures are tabled and discussed, with various economic impacts around the galaxy.
Different voting blocs have different power levels, and eventually an analog of the UN security council can be established. It's a great maneuver, allowing you to If you're clever, you can make yourself a permanent member... then you can lower the number of members to one... then, well - you ARE the Senate.
The strategy can be achieved by building up a truly massive store of favors from other empires, then maneuvering the player empire into the position of being the only permanent council member. Once that's done, the size of the council is slowly... slowly reduced. Opposition to the final vote will be huge, so you cash in the massive store of favors for a huge boost to your political power. Congratulations! You are the Senate now.
Stellaris: Federations is the newest expansion to Paradox Development Studio's sci-fi grand strategy 4x Stellaris. It introduces a wide range of new features, including new types of Federation alliances and the Galactic Community. You can learn more about Federations at Paradox's official website.
Thanks, Reddit user Skyelarkey, for realizing this could be done and then doing it.