For many Americans today, the term special prosecutor is likely to call to mind Watergate, Kenneth Starr’s investigation of Bill Clinton, perhaps the Iran-Contra Scandal and, of course, Robert Mueller’s investigation of Russian interference in the 2016 presidential election. But those investigations grew out of a rich, complicated and not always edifying history that even most legal scholars and historians have largely forgotten. Between 1875 and 1973, five different presidents appointed special prosecutors to investigate all manner of high-level official corruption.

These investigations span nearly a century, during which American society and governmental institutions underwent enormous, transformational changes. Even so, they share much in common. In each case, popular outcry over alleged misconduct by high executive officials forced the President to appoint a special prosecutor to restore public confidence. In each case, the high public salience of the resulting investigation gave the President’s supporters powerful incentives to attack the special prosecutor. But the special prosecutor’s visibility also provided the American people a potent tool for holding Presidents accountable. In each case, the willingness and ability of the American people to impose a political price on the President proved decisive.

This factor proved key right from the beginning.

On the morning of Saturday, February 12, 1876, an illustrious visitor arrived at the White House to perform an unusual duty. The visitor was chief justice of the United States Morrison Waite. The duty was to preside over the deposition of President Ulysses S. Grant. Never before or since has a sitting president testified on behalf of a defendant in a federal criminal prosecution. Grant’s cabinet had unanimously counseled him against doing so. But his beloved chief of staff, Orville Babcock, was facing federal bribery charges in St. Louis, and Grant could not be dissuaded.