muckraker: a journalist or other person who hunts for and publishes scandalous information
Muckraker was popularized by Theodore Roosevelt, who used it in a 1906 speech, saying, "the men with the muck rakes are often indispensable to the wellbeing of society, but only if they know when to stop raking the muck . . ." Roosevelt was referring to investigative journalists whose articles very popular with the early twentieth-century reading public. He drew on a character in the 1675 allegory Pilgrim's Progress, "the man with the muck rake" who can only look down. When offered a celestial crown in exchange for his muck rake by one who stood above him, he did not look up, but continued to rake up bits of straw and sticks.
Although muckraker is often considered insulting, Roosevelt approved muckrakers to some extent. Upton Sinclair's prototypical muckraking novel, The Jungle, exposing horrendous conditions in the meatpacking industry, is at least part of what led Roosevelt to support the Pure Food and Drug Act of 1906.