From Robert Reich BlogIt won't be easy to impeach Donald Trump. No president in American history has ever been convicted on articles of impeachment. Only two presidents so far have been impeached by the House and had that impeachment go to the Senate for trial. The first was Andrew Johnson, in 1868, when the Senate came one vote short of convicting him. The next was 131 years later, in 1999, when Bill Clinton's impeachment went to the Senate. Fifty Senators voted to convict Clinton, 17 votes short of what was needed.
What about Richard Nixon? He resigned early in this process, before the House had even voted on articles of impeachment. And then his successor, who had been his vice president, Gerald Ford, gave Nixon a full and unconditional pardon for any crimes he might have committed against the United States while president.
This isn't to say Trump couldn't or won't be impeached. Only that it's a long and drawn-out process.
It all revolves around Article I, Sections 2 and 3 of the Constitution, and rules in the House and the Senate implementing those provisions.
Step 1. It starts in the House Judiciary Committee, when a majority of the members vote in favor of what's called an "inquiry of impeachment" resolution.
Step 2. That resolution goes to the full House of Representatives where a majority has to vote in favor. And then votes to authorize and fund a full investigation by the Judiciary Committee into whether sufficient grounds exist for impeachment.
Step 3. The House Judiciary Committee investigates. That investigation doesn't have to be from scratch. It can rely on data and conclusions of other investigations undertaken by, say, the FBI.
Step 4: A majority of the Judiciary Committee members decides there are sufficient grounds for impeachment, and the Committee issues a "Resolution of Impeachment," setting forth specific allegations of misconduct in one or more articles of impeachment.
Step 5: The full House then considers that Resolution and votes in favor of it -- as a whole or on each article separately. The full House isn't bound by the Committee's work. The House may vote to impeach even if the Committee doesn't recommend impeachment.
Step 6: The matter then goes to the Senate for a trial. The House's Resolution of Impeachment becomes in effect the charges in this trial.
Step 7: The Senate issues a summons to the president, who is now effectively the defendant, informing him of the charges and the date by which he has to answer them. If the president chooses not to answer or appear, it's as if he entered a "not guilty" plea.
Step 8 is the trial in the Senate. In that trial, those who are representing the House -- that is, the prosecution -- and counsel for the president, both make opening arguments. They then introduce evidence and put on witnesses as in any trial. Witnesses are subject to examination and cross-examination. The trial is presided over by the chief justice of the Supreme Court -- who has the authority to rule on evidentiary questions or may put such questions to a vote of the Senate. The House managers and counsel for the president then make closing arguments.
Step 9: The Senate meets in closed session to deliberate.
Step 10: The Senate returns in open session to vote on whether to convict the president on the articles of impeachment. Conviction requires a two-thirds vote by the Senate. Conviction on one or more articles of impeachment results in removal from office. Such a conviction also disqualifies the now former president from holding any other public office. And it doesn't bar additional legal proceedings against that former president, and punishment.