The first thing to understand is that conflicts between the branches, like those between President Trump and Congress, are nothing new.
“Lawmakers and presidents have found ways to resolve these disputes in the past,” says former Senator Carl Levin, a Democrat from Michigan. “That’s not to say Congress and the White House haven’t battled over congressional inquiries.”
When they do butt heads, there are several options: The two branches may fight it out politically, meaning they try to exert political pressure on each other in an effort to persuade. They can also turn to the third branch for a solution.
That’s what happened during the Watergate scandal that eventually prompted President Richard Nixon to resign in 1974 (see “When Branches Clashed,” below). When Congress was investigating Nixon’s involvement in a cover-up of Watergate, they asked the White House to hand over recordings of Oval Office conversations. When the White House refused, Congress went to the courts. The Supreme Court ruled unanimously, in United States v. Nixon, that the president wasn’t above the law and had to hand over the tapes to Congress.
The recordings showed that Nixon had obstructed justice—an impeachable offense.
Impeachment is the tool the Constitution provides for removing from office a president (or other federal official) who has committed “treason, bribery, or other high crimes and misdemeanors.” It requires the House of Representatives to conduct hearings laying out the evidence and then to vote to impeach. The president is removed from office only if two-thirds of the Senate votes to convict him.
That has never happened. Two presidents have been impeached by the House—Andrew Johnson in 1868 and Bill Clinton in 1998—but both were acquitted by the Senate and remained in the White House. In Nixon’s case, once it became clear that there was enough support in Congress to remove him from office, he resigned.
“Impeachment is the nuclear weapon that Congress always has,” says John McGinnis, a law professor at Northwestern University in Illinois. “But there are dangers in using that weapon.”