The noble career are the S:4 CotI politicians, at least in the Imperium.
I fully agree, if we're talking about politics at subsector level and up.
As for a single planet politics, it would depend on the government class:
- Bureaucreat could be ok in most (if not outright all) cases
- Diplomat will also serve in most cases (and even more in a gov 7 planet)
- If gov is 6 (or B or C) the military could be the politicians (mostly if it represents military rule)
- if government is 2 anyone can be involved in politics. If 4, any background might also
- On gov 3 or C it also may depend more on SOC than on previous career...
- Even scientist could be involved in politics if the government is 5
As an example (albeit MT, but I guess could be used for CT too), in Challenge #45 Toll Road adventure (pages 14-20) we're presented the main political leaders on a gov 4 world. Among them there's one ex-Navy (planetary), one ex-army, one ex law enforcer agent, one ex-merchant and one bureaucrat...