You don’t need a special degree to become a political officer. Like in other career tracks within the Foreign Service, diplomats learn the necessary skills after they’re hired and mostly on the job.
Lots of aspiring diplomats want to become political officers. It may be more difficult to enter the political track than some others because—according to the (incomplete) data that’s available—you need a relatively high score on your entry exams to get in. On the other hand, exactly how difficult it is depends on a variety of factors, like the hiring rates and the number of positions available at any given time. There’s no official source that confirms that it is currently more or less difficult than other career tracks.
The political career track might be the more natural choice for people who are analytical and like to (learn how to) produce high-quality written reports. Political officers do a lot of “brain work,” like researching, analyzing, and debating, to get a good sense of the main issues in a country, including the historical context. They have to make sense of complex issues within a short amount of time.
I think political officers also need a certain level of confidence. They have to be—or get—comfortable initiating conversations with people they don’t know and discuss complicated matters, often in a foreign language. They also need good personal skills.
Being extremely interested or specialized in one specific topic or region can be both helpful and problematic. Political officers are often able to pick assignments that match their interests and skills, especially if they stand out in them. Obviously, highly skilled and motivated individuals are chosen to fill top positions in their respective areas.
On the other hand, diplomats need to be flexible and adaptable because there’s a (very) good chance they end up serving in places and positions they never imagined for themselves. Also: policy priorities may change and you might wake up one day and find out that the thing you always wanted to work on is out of fashion.