Thus far, nearly two-and-a-half centuries into the nation's history, only four presidents have been faced impeachment proceedings. The first, as described in the introduction, was Andrew Johnson, the second was Richard Nixon and the third was Bill Clinton. The fourth was Donald Trump, who also is the only president in U.S. history to be impeached twice during the same four-year term [source: Pramuk].
In the case of Andrew Johnson, Congress passed a piece of legislation called the "Tenure of Office Act," which was designed to stop the president from firing a cabinet member without Congress's approval. It's pretty clear they were hoping he would break this law and it should be noted that the act was later struck down as unconstitutional. But while it lasted, it served its purpose because Johnson duly fired his Secretary of War and the House quickly issued Articles of Impeachment. As we said earlier, the effort to get rid of Johnson was doomed to fail by just one vote.
Richard Nixon's presidential career began to nose-dive after it was discovered that he and his administration used a variety of dirty tricks and illegal methods to sabotage the Democratic party, most notably breaking into the Watergate hotel. When he lost the support of his own party, it became clear that he would likely be impeached and almost certainly removed from office. But Nixon deprived Congress of that satisfaction and, in a "you're-fired-I-quit" scenario, he resigned.
Bill Clinton was infamously caught perjuring himself when he lied to a grand jury about his relationship with White House intern Monica Lewinsky. On the strength of that perjury, the Republican-dominated House of Representatives voted to impeach him on Dec. 19, 1998. The proceedings then moved to the Republican-led Senate in January 1999. Because the constitutional wording for trials of impeachment in Article 1, Section 3 are so brief, there are no set rules as to how the Senate trial must proceed. Essentially, the senators made it up as they went along.
For instance, during Clinton's impeachment trial, the Senate decided to give the "managers" only four days to present their case and the president's defense team four days to defend him. As for witnesses, it wasn't even clear if any would be permitted to testify at all. Eventually a few gave videotaped depositions [source: Savage].
The fact that the Senate, which essentially serves as the jury in these proceedings, can determine the rules of the trial, underlines how unique a process impeachment is. It's hard to imagine a jury in a criminal case dictating how long an opening statement can be. In any case, the impeachment process foundered when the Senate acquitted Clinton with a 50-50 vote, far short of the two-thirds required to convict [source: Savage].
On Dec. 18, 2019, the House of Representatives voted to impeach Donald Trump on two articles of impeachment, one for abuse of power and one for obstruction of Congress after a CIA whistleblower lodged a complaint about a phone call between Trump and newly elected president of Ukraine Volodymyr Zelensky. On the call, Trump pressured Zelensky for help in smearing political rival Joe Biden. Several more diplomats and administration officials confirmed the call [sources: Fandos and Shear]. In the Senate trial, no witnesses were called and no documents were subpoenaed. Ultimately, Trump was acquitted by the Senate on Feb. 5, 2020.
Barely a year later, on Jan. 13, 2021, the House of Representatives voted to impeach Donald Trump for a second time for insurrection. This time Trump was charged with inciting his supporters to assault the U.S. Capitol on Jan. 6, 2021, where five people were killed. Ten members of his own party voted "yes" on impeachment. As of this writing, Trump's presidency is over and Joe Biden has been inaugurated. The House has not yet sent over the article of impeachment to the Senate. So is there precedent to convict a president who's already left office? According to the Wall Street Journal, no.
But in 1876, the House and Senate agreed they do have the power to impeach former government officials. And they did just that when they continued with the impeachment and trial of President Ulysses S. Grant's War Secretary William Belknap, who resigned minutes before being impeached for corruption. "The Senate convened its trial in early April, with Belknap present, after agreeing that it retained impeachment jurisdiction over former government officials. During May, the Senate heard more than 40 witnesses, as House managers argued that Belknap should not be allowed to escape from justice simply by resigning his office," according to the Senate Historian website.
As far as Trump's second impeachment trial in the Senate goes, as of this writing, House Speaker Nancy Pelosi has not said publicly when she plans to send the impeachment article to the Senate. But the Constitution requires the Senate to begin the trial at 1 p.m. EST the next day.