Now that Nancy Pelosi has announced an official impeachment inquiry into President Trump’s July 25 phone call in which he invited Ukrainian President Volodymyr Zelensky to do Trump the “favor” of investigating his political opponents, people are wondering: What will an impeachment process actually look like?

To answer this question, there are two places to look for guidance: the U.S. Constitution and the historical precedent of prior impeachment proceedings.

It turns out there are three impeachment clauses in the U.S. Constitution.

Article II, Clause 4, contains the “high crimes and misdemeanors” language that everyone is talking about these days: “The President, Vice President and all civil officers of the United States, shall be removed from office on impeachment for, and conviction of, treason, bribery, or other high crimes and misdemeanors.”

Article I, Section 2 states that “[t]he House of Representatives … shall have the sole Power of Impeachment.”

As a practical matter, what this means is that the House issues the congressional equivalent of an indictment. It decides the contents of the articles of impeachment—a list of wrongdoing that, in the House’s view, amounts to “high crimes and misdemeanors.” Note that the Constitution does not state how many House members must vote to impeach in order for the articles to stick and move to the Senate, and it doesn’t define what a high crime or misdemeanor is for purposes of impeaching a president.

Once the House issues articles of impeachment, Article I, Section 3 provides that “[t]he Senate shall have the sole Power to try all Impeachments,” and that “[w]hen sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.”

So, for Trump, Chief Justice Roberts would preside over a “trial” in the U.S. Senate, any witnesses who are called in that proceeding must testify under oath, and two-thirds of the Senate (the congressional equivalent of a jury) must vote to remove the president from office—a calculus that, these days, would require at least 20 Republicans to vote along with all Senate Democrats.

Unlike a criminal trial, however, a conviction in the Senate on articles of impeachment cannot result in jail time. Article I, Section 3 adds that “Judgment in Cases of Impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.” So long as the statute of limitations has not run on any relevant crimes, therefore, an impeached and removed Trump could be prosecuted as a private citizen for any wrongdoing that gave rise to his impeachment.

Andrew Johnson and Bill Clinton are the only presidents to be impeached and face a Senate trial. The House introduced articles of impeachment against Nixon but he resigned before actually being impeached. The Nixon and Clinton cases, though, are both useful to show what could happen next.

The Constitution does not require that the House actually hold an official vote in order to begin an impeachment investigation, although it’s arguably important so that House members don’t plunge presidents into ongoing “impeachment” proceedings just for political gain. For both Nixon and Clinton, an initial vote did take place. And in both instances, articles of impeachment began with approval in the House Judiciary Committee and then moved to the full House of Representatives for a vote.

For Bill Clinton, 13 House prosecutors began the Senate trial on January 19, 1999, with three-days of opening statements. Following the Clinton team’s three-day response, senators then questioned the prosecution and defense teams for two days, passing written questions through then-Chief Justice William Rehnquist. Note that in civil and criminal trials, the jury does not have an opportunity to question the lawyers.

Next, senators heard arguments about dismissing the charges against Clinton and considered whether to obtain testimony—called “depositions”—of certain witnesses, including former White House intern Monica Lewinsky. Eventually, a number of witnesses were questioned by House prosecutors behind closed doors. The Senate deliberated in secret. After closing arguments from both sides, the Senate voted to acquit on February 12, 1999—less than a month after the proceedings began.

For Nixon, things went more quickly. The House Judiciary Committee adopted three articles of impeachment in late July 1974, and Nixon resigned on August 9, 1974.

Before the impeachment proceedings for both Nixon and Clinton, investigations had already been conducted by a special prosecutor (Nixon) or an independent counsel (Clinton), who were appointed by the attorney general or a three-judge panel, respectively. For Trump and the Ukraine scandal, there is no such prosecutorial roadmap of facts and law. Unless the House picks up the Mueller report as part of its inquiry—which is unlikely, given the time crunch before the November 2020 election and the nation’s collective shrug about Russian interference in the 2016 election at this point—all of the investigation will have to happen in Congress, if at all.

This leaves a lot of leeway for the White House to continue to stonewall responses to document requests and calls for witness testimony. In criminal investigations and trials, judges don’t tolerate such shenanigans for long. Congress can enforce its subpoenas, too, but the process can be laborious and time-consuming (although we can expect expedited review for purposes of moving the impeachment process along).

Finally, in a criminal trial, the burden of proof—that is, the threshold of evidence that prosecutors must establish in order to convict—is beyond a reasonable doubt. The Constitution is silent about the standard for impeachment, leaving it to individual senators to decide for themselves how much convincing they need, unless the Senate as a whole can agree to apply a single standard. A much lower standard would be a preponderance of the evidence, meaning that a senator could decide to remove Trump with only 51 percent certainty that he committed “high crimes and misdemeanors.”

Applying something lower than proof beyond a reasonable doubt makes sense for removal of a president. The highest standard of proof—like the presumption of innocence—applies in criminal trials for good reason: If it wins a conviction, the government can put someone in jail or even execute them.

Impeachment, by contrast, is about a pink slip. The president gets fired. No president has never actually been removed by the Senate in our nation’s history, but the impeachment clauses are there for a good reason—as in any job, some employees just turn out to be bad apples. Regular people understand that, in order to stay employed, they must diligently follow rules and do good work. If not, they could feel the consequences of unemployment.

The impeachment clause exists to ensure that the person sitting in the Oval Office is ultimately no different from the rest of us in this regard. Clearly, Trump doesn’t understand this. At least not yet.