excessive enthusiastic or intensely devoted to something
rabid - wild
The term ‘rabid’ was originally used to refer to an animal acting in a frenzied manner due to a rabies infection. It has since been adapted to describe a person who is deemed to be behaving in a similarly wild and irrational way, particularly with regards to their support for or beliefs about something. Often used in connection with politics.
Julie is a rabid proponent of that policy. She has been fighting for years to have it enshrined in law.
That football team inspires intense devotion. The rabidness of their supporters is almost unparalleled.
The politician reiterated her strong support for institutional reform, but denied accusations that she was rabidly-left wing.