Speaker Nancy Pelosi, D-Calif., has called on Vice President Mike Pence to initiate the 25th Amendment process to remove President Donald Trump from office. Pelosi suggested that the House will likely impeach Trump based on his role in this week’s attack on Congress if Pence does not act. According to Assistant Speaker Katherine Clark, D-Mass., the House will vote on impeachment articles next week.

But Democrats’ bid to impeach Trump before he leaves office is not possible under the rules. The Senate cannot begin a trial in its current procedural posture – much less end one – before Trump’s term as president expires. And Congress can’t impeach Trump once he has left office.

The House has “the sole Power of Impeachment” under the Constitution (Article I, section 2, clause 5). That means that it must initiate the impeachment process. However, the Constitution gives the Senate “the sole Power to try all Impeachments” (Article I, section 3, clause 6). Consequently, removing Trump from office requires both House and Senate action.

A trial begins when the House sends articles of impeachment to the Senate. Specifically, Rule II of the Senate’s Rules of Procedure When Sitting On Impeachment Trials stipulates that trial proceedings begin once the House managers arrive at “the bar of the Senate” to present their articles of impeachment. After submitting the articles, the House managers withdraw. The Senate then takes steps to organize itself for the upcoming trial (i.e., administer oaths, notify the Supreme Court’s Chief Justice that he must preside when the House impeaches a president, etc.).

The Senate must be in session to receive the House’s articles of impeachment. Rule IX of the Standing Rules of the Senate stipulates that messages (i.e., articles of impeachment) “may be received at any stage of proceedings, except while the Senate is voting or ascertaining the presence of a quorum, or while the Journal is being read, or while a question of order or a motion to adjourn is pending.” But senators routinely circumvent Rule IX’s prohibition on receiving House messages “during a recess…pursuant to an order of the Senate, and by unanimous consent.”

Yet even if it receives articles of impeachment from the House, the Senate cannot begin the trial until January 20. This is because the Senate is not currently in session. It will next convene in pro forma sessions on January 8, 12, and 15 before reconvening in regular session again on January 19. And the unanimous consent agreement that set up the pro forma sessions explicitly bars the Senate from conducting business.

Absent unanimous consent, the Senate cannot begin an impeachment trial before 1 pm on January 20. Rule III of the Senate’s impeachment rules stipulates that when the Senate receives articles of impeachment, it “shall, at 1 o’clock after noon of the day (Sunday excepted) following such presentation, or sooner if ordered by the Senate, proceed to the consideration of such articles.” The unanimous consent agreement to set aside the Senate’s rules regarding pro forma sessions supersedes any provisions of those rules that requires senators to begin an impeachment trial.

This timeline makes Democrats’ impeachment effort moot because Trump will no longer be in office when the Senate can begin a trial under its rules. The 20th Amendment to the Constitution stipulates, “the terms of the President and Vice President shall end at noon on January 20.” In other words, President-elect Joe Biden will be sworn in as president one hour before the Senate can begin Trump’s impeachment trial. And once Biden is president, Trump is no longer subject to impeachment.