In matters of Halacha, I defer to my rov and/or Gedolei Hador. In matters of politics, I think for myself. Chances are that if a Gadol has very strong feelings about a given politician, I most likely already share those same feelings, but that is not Torah m’Sinai.
Even a rov can have a personal bias that might influence his decision to prefer one candidate over another, and that bias might not always necessarily be for the general long term good. I would want to know WHY the Gadol chose that specific candidate for endorsement, if I did not care for the same person, and perhaps my opinion would change, if there were a compelling reason.