We receive this number just about daily - sometimes 2-3 times per day

These people are extremely annoying

I called this number back... interestingly enough... it registers busy.  They call... leave no message. Don't know who they might be.

This number just called. I did not answer.

I am assuming it is politically motivated (exempt from do not call), which gets "kicked" by my system (all they get is a recording).

Just got the same call, picked it up and no answer.