Let me pose a thought experiment to you.
You are a powerful reality-warper who has the ability to mind-control people, travel through space unaided, survive almost any physical conditions, and change shape at will (though you have to go through a year-or-so long process to change what those forms are). You can, essentially, do anything you want. Except this is also true of everyone else around you, because this is just kind of how your species is built. (Everyone isn't necessarily built like this, of course - aliens are aliens. Some aliens are much more powerful reality-warpers, and some are much less, or they don't warp reality at all.)
You want Ultimate Power™.
There are only a few ways to get it, because mind-control is frowned upon for political expedience in the broader galaxy, and there are more than enough people hitting above your weight class that you can't just waltz in, force people to agree with your whims, and walk out with Ultimate Power™. You'll get thrown into the Space Hague in like, five minutes, if someone doesn't outright kill you for the insolence. Not everyone can shake it off, but enough people can, when you're getting into the realms of Ultimate Power™
Similar laws govern the legality of using mind-control to rig elections and semi-legally get you involved in the political arenas that get you involved in Near-Ultimate Power (which is, natch, good enough for you). You can't do that either.
If you really want Ultimate Power™, you have to work with a coalition, which is true of basically everyone after Ultimate Power™. This isn't the end of the world. Having a coalition working for Mutual Ultimate Power™ means that you guys can all share in the spoils, once you have them. The problem is still having them. Even working together, it's still difficult to successfully grab and hold power, isn't it?
There are very few ways to take power, and doing it legitimately is a sucker's game. The only accessible pathway to true power is through building a majority party that will acquiesce to your demands within a pre-existing intergalactic governing body of planetary and planet-system governments (we'll call it the Inter-Galactic Senate, ISG for short; this is backstage so no names are set in stone). Representatives in the ISG get their votes for each member state they represesnt. You want to gain position in the ISG by being "elected" as a representative. You can be the representative for multiple planets or planetary systems, but pretty much every member so far is already spoken for.
The obvious move is to find a non-member planet with aliens on it and convince them to elect you their ISG representative. Or, you know, "convince", and, you know, "elect". Heh heh. Whatever gets you your Ultimate Power™.
And naturally - the more the merrier. Every planet you can pull under your sway gets you a little closer to the goal.
Any overt use of mind-control will still get you tossed into the Space Hague.
You have essentially-unlimited material resources, including money for mercenaries, aid, and organizations. You have all the time in the world.
There are only two conditions.
You cannot appear "evil" (no force-backed dictatorships beating votes in favor out of people)
These people must not only back you at exactly the right moment, but every other time they're called upon, they must always stay in support of you.
