You must understand that AdSense has a relevant category of as News, Media & Publications and sensitive categories that may fit your development such as Politics and Religion.
Keep in mind with AdSense, even though you’re using niche specific categories, ads are also served on the users past searches, likes, preferences, etc. For instance, when I visit a website with AdSense on it about cats, I will see ads for Onamae. This is also due to the fact that I am geographically located in Japan and that is the GoDaddy of Japan (maybe?).
Serving up relevant ads strictly about politics may be good, but it could also hinder the possible click-through-rate and cost-per-click that you receive.
With the example of cats, if they served ads about cat food, I wouldn’t click. I buy my cat food at a store. However, if I see an Onamae special on domain names, I may be more apt to click it. The cat food may pay $0.10 CPC, whereas the domain related ad pays $2.50 (did not research these exact amounts).
As you can see, you can have high CPC/low CTR, high CPC/high CTR, low CPC/low CTR. Google AdSense optimizes your pages based on the visitors automatically and you can adjust the underperforming categories to not display.
AdSense isn’t the only way to go, but there isn’t a dead end for monetizing your site.
Good luck!