In 1972, an early frontrunner for the Democratic presidential race named Edmund Muskie became a victim of dirty politics. Allegations of Muskie's wife being an active alcoholic were made ... a good example of dirty politics. Muskie's emotional defense of his wife made him appear weak and vulnerable. And he lost. Dirty politics is an intrusive investigations into opponent's personal life. And IRS audits by an incumbent president. President Richard Nixon maintained an entire staff of experts in dirty politics ... including Donald Segretti and a young Republican named Karl Rove. Political enemies of the president were routinely audited for years. And we know how Richard Nixon finished his last days of Presidentship.
It could be said that politics is not too far removed from cross examination in a court room. In court, a lawyer on cross exam is to do everything in their power to discredit the witness. This is like cross examination. And the politicians are the witnesses.