an underhanded attempt to gain power
underhanded
/ˌən-dər-ˈhan-dəd/
adverb
underhand
adjective
marked by secrecy, chicanery, and deception : not honest and aboveboard : sly
secret covert stealthy furtive clandestine surreptitious underhanded mean done without attracting observation. secret implies concealment on any grounds for any motive. covert stresses the fact of not being open or declared.