the.com/whispering campaign

means An organized effort to spread damaging rumors or negative information about someone quietly and indirectly, rather than through open, attributable statements.

from The phrase joins 'whisper' — speech kept deliberately low and secretive — with 'campaign,' borrowed from military language for a coordinated, sustained operation. It emerged in early 20th-century political and public-relations usage, describing the tactic of spreading damaging claims mouth-to-mouth so no single speaker could be pinned down or sued for it. The 'whisper' part is literal in spirit even if not in volume: the point was always deniability, information passed so informally that its origin dissolved.