In the US, the modus operandi for a candidate determined to win an election is to dig up dirt on one or more of their opponents. In order to help them achieve this end, candidates will resort to hiring private investigators or seeking assistance from their campaign managers, who will perform in-depth opposition research
Opposition research (also called oppo) is the practice of collecting information on a political opponent or other adversaries that can be used to discredit or otherwise weaken them. The information can include biographical, legal or criminal, medical, educational, or financial history or activities, as well as prior media coverage, or the voting record of a politician. Opposition research can also entail using "trackers" to follow an individual and record their activities or political speeches.
Until recently, I had never read of a company who explicitly advertised itself for this type of role, it would be rather counterproductive as the need for secrecy is of the utmost importance, and naturally, their employers would be anxious to avoid lawsuits at all costs.
However, with the recent sexual misconduct scandals that have afflicted the world of Hollywood and Washington, it appears there are secret organisations that offer their services to dig up dirt on individuals who are completely disconnected from the world of politics and espionage.
From The New Yorker, in an article written by Ronan Farrow, in November 6, 2017
Harvey Weinstein’s Army of Spies
…Harvey Weinstein set out to suppress allegations that he had sexually harassed or assaulted numerous women. He began to hire private security agencies to collect information on the women and the journalists trying to expose the allegations. According to dozens of pages of documents, and seven people directly involved in the effort, the firms that Weinstein hired included Kroll, which is one of the world’s largest corporate-intelligence companies, and Black Cube, an enterprise run largely by former officers of Mossad and other Israeli intelligence agencies. Black Cube, which has branches in Tel Aviv, London, and Paris, offers its clients the skills of operatives “highly experienced and trained in Israel’s elite military and governmental intelligence units,” according to its literature.