This week the House Judiciary Committee received Congressman Adam Schiff’s report and proceeded to begin drafting articles of impeachment. Because this is only the fourth presidential impeachment in American history there is not a lot of precedent for what constitutes an impeachable offense. Nonetheless, the previous three impeachments give us some idea of the kinds of issues the Judiciary Committee will be dealing with.
The big issue is whether the articles of impeachment should be narrow or broad: should they deal with specific violations of the law on the part of the president or with broader constitutional issues?
In the very first impeachment—that of President Andrew Johnson—the first eight articles accused the president of violating the Tenure of Office Act. This was a law, passed over Johnson’s veto, which prevented a president from removing office holders without consent of the Senate. When Johnson removed the Secretary of War from office (who at that point was charged with carrying out reconstruction) without Senate consent, the Republican Party began impeachment proceedings. The ninth article dealt with a violation of another law, the Military Appropriations Act. The issue behind the personnel changes was how to carry on after the Civil War. Johnson sided with Democrats who advocated leniency towards the South and restrictions on the civil rights of the freed slaves. This put him at odds with most of the Republican party.
But the Radical Republicans, (so called because they were the most ardent defenders of the rights of former slaves and for holding the South accountable for the war) argued for a more sweeping article of impeachment. In her comprehensive history of the first impeachment, Brenda Wineapple writes,
“These articles, even the ninth, didn’t satisfy Thaddeus Stevens who didn’t want impeachment defined in such crabbed terms. An impeachable offense need not be an indictable one, like pocketing the spoons.” 
Under pressure from Senator Thaddeus Stevens (R-Mass.), leader of the Radical Republican faction in the Senate, the House adopted two more articles of impeachment. The first accused the president of disgracing his office by making speeches that “… did attempt to bring into disgrace, ridicule, hatred, contempt and reproach, the Congress of the United States.” This article seems quaint in today’s rhetorical environment where ridicule, disgrace and downright hatred of one’s political enemies is an everyday occurrence.
The final article of impeachment accused the president of disregarding the Constitution, by denying that the “legislation of said [the 39th] Congress was valid or obligatory upon him.”  Johnson was insisting that the 39th Congress was illegitimate because it did not include the southern states—a controversial claim not shared by most of the sitting Congress. With this argument the final article went to the heart of the constitutional conflict in a way that none of the other articles did, by asserting that the president could not defy Congress because they were equal branches of government.
When it came to the trial in the Senate, the Johnson impeachers allowed themselves to get bogged down in arguments about the Tenure of Office Act, leading Wineapple to conclude,
“Legal casuistry had dwarfed the real meaning of impeachment and its implications, all of which, again, had to do with responsibility: the responsibilities of a President, …the responsibilities of Congress and its relationship to public order.”
The impeachers of Richard Nixon, perhaps learning a lesson from the first impeachment even though it took place more than 100 years before, kept the three articles of impeachment focused on the broader constitutional questions. This gave rise to what has since become a Washington, D.C. maxim: “It’s the cover-up, not the crime.” For while the actual break-in at Democratic Headquarters is mentioned in Article I, the article itself focuses on actions taken (with Nixon’s approval) that attempted to obstruct justice. In Article 2 the House accused Nixon of
“substituting his judgement as to what materials were necessary for the inquiry, interposed the powers of the presidency against the lawful subpoenas of the House of Representatives, thereby assuming for himself functions and judgements necessary to the exercise of the sole power of impeachment vested by the Constitution in the House of Representatives.”
And in Article 3, the final article approved by the Judiciary Committee, the Nixon impeachers accused him of contempt of Congress—in essence, the same charge Johnson’s impeachers had leveled in their final article of impeachment.
The third president to be impeached, Bill Clinton, was the subject of only two articles of impeachment. Both focused on his offering “perjurious, false and misleading testimony,” first to a grand jury and then in a federal civil rights action brought against him. But compared to the first two impeachments, the Clinton impeachment is thin gruel. (A third article on abuse of power was defeated on the House floor.)
Which brings us to the all-important question of circumstance.
The Andrew Johnson impeachment was, at its heart, about one big issue: the nature of Reconstruction of the Union after the Civil War, which hinged upon the issue of full citizenship for the newly freed slaves. In his trial, Johnson was acquitted by one vote but he was not re-nominated, nor was he re-elected for a second term. And yet, a mere 8 years later, the vision of Reconstruction Johnson advocated for came to be as Union troops pulled out of the south and former slaves remained without full civil rights.
The essence of the Nixon impeachment was the paranoia of the president himself and the belief that the president was more powerful than he in fact was. Nixon didn’t need illegal activities in order to beat the Democrats in 1972, especially once they had nominated Senator George McGovern. Without Watergate, Nixon’s presidency would probably rank in the above average range for his openings to China, his creation of the Environmental Protection Agency and other major policy successes. But a paranoid mindset led the president and his men to take a variety of steps that became, in the famous words of White House Counsel John Dean, “a cancer on the presidency.”
Clinton’s impeachment and subsequent acquittal took place in the least consequential context of all. His sexual indiscretions with an intern simply didn’t rise to the level of high crimes and misdemeanors. Clinton did not use federal money to seduce Monica Lewinsky. She was not a Russian spy photographing sensitive materials off the president’s desk during their liaisons. She was just a young woman interning in the White House. During and after the Clinton impeachment, not one but two Republican leaders had to give up their posts because of their own sexual misadventures. Clearly, this was not to be an impeachable offense.
The Trump articles of impeachment will, most likely, resemble the Nixon articles of impeachment. Three of the four constitutional scholars who testified this past week focused on the constitutional issues. The actions described in the Mueller report can easily be interpreted as obstruction of justice. Trump’s withholding of aid to the Ukrainians can easily be interpreted as abuse of power and bribery. And his refusal to hand over White House documents along with his orders that staff not testify are clear attempts to assert presidential power over congressional power—actions that go to the heart of the constitutional separation of powers. The House will likely consider this obstruction of Congress.
 Note: Stevens was a Republican Senator from Massachusetts and leader of the Radical Republicans. Brenda Wineapple, The Impeachers: the Trial of Andrew Johnson and the Dream of a Just Nation, (New York, random House, 2019) p. 265.
 Opcit, p. 316.
 Speaker of the House Newt Gingrich (R-Ga.) and Speaker-designate Bob Livingston (R-La.)