Before Watergate it was generally understood that former presidents were subject to criminal prosecution while sitting presidents must first be impeached and removed from office.
The battle for the tapes continued until the Supreme Court delivered the coup de grace in United States v. Nixon, ordering the president to produce the tape recordings subpoenaed by the special prosecutor. For all intents and purposes, the 8-0 decision ended the Nixon presidency. It was followed in short order by the release of the tapes (including the smoking gun tape), the House Judiciary Committee’s vote on impeachment, and Nixon’s resignation.
Congress subsequently passed a wide range of reform legislation. To insulate prosecutors from presidential interference, Congress enacted the Ethics in Government Act of 1978 which set up a novel process for appointing independent counsel. New election laws established the Federal Election Commission and limited campaign contributions and expenditures. The Tax Reform Act of 1976 had provisions responding to Nixon’s misuse of information collected by the IRS. Amendments to the Freedom of Information Act empowered judges to review classified materials, and the Civil Service Reform Act of 1978 enhanced protections for government whistleblowers.
The irony of Watergate is that, in responding to Nixon’s abuse of power, the Supreme Court, the House Judiciary Committee, and the special prosecutor set several precedents that have since made it harder to check the abuse of presidential power.
The Supreme Court’s interpretation of executive privilege may qualify as the supreme irony. Before Watergate the constitutionality of executive privilege was an open question. Nixon was not the first president to block Congress and the courts from hearing testimony of executive officials or obtaining documents. President George Washington withheld documents lawmakers requested relating to a botched military expedition. In modern times, President Dwight D. Eisenhower stands out for refusing to allow subordinates to testify in the McCarthy hearings. Yet the Supreme Court had never recognized the constitutionality of executive privilege until United States v. Nixon. The uncertainty surrounding executive privilege prior to that decision is obvious in comments Nixon made to Haldeman. Focusing on public relations, as was his wont, he worried that “privilege” was a “very bad word,” because “it means we’ve got something they don’t have.”
In his investigation of Trump, Mueller felt bound by a Justice Department opinion issued during the Watergate scandal that concluded that a sitting president cannot be indicted.