Applying to a top-program, but for a sub-field that program is not strong in
There is no way to know. Some departments may rank candidates independent of their desired specialty while other departments may weight who the applicant wants to work with (and who wants to work with the applicant) heavily. For departments who give weight to the sub-field, the department might be trying to strengthen a weakness or only accept students in areas they are strong.

I am not really sure why the departmental politics matters. Trying to deceive (in a mild way) the admissions committee is not likely going to be advantageous. Your strongest application is going to be to talk about the area you are most excited about. Further, if you get accepted based on a falsely expressed interest in A, you may not be able to switch to B later.