Vice president-elect Mike Pence arrives at Trump Tower in New York City, Dec. 15, 2016. Getty

Though Donald Trump is set to be inaugurated as the 45th president of the United States on Friday afternoon, it’s not out of the realm of possibility that the title could eventually go to Vice President-elect Mike Pence. In the potential case of Trump’s impeachment, death or resignation, Pence would be next in line to become commander-in-chief.

The 25th Amendment to the Constitution states that “in case of the removal of the President from office or of his death or resignation, the Vice President shall become President.” The office of the vice president was initially established to provide a successor to the president in the event any of those things occurred.

According to the constitution, a president can be impeached for “treason, bribery, or other high crimes and misdemeanors.” Trump would have to be impeached and convicted in order for Pence to take his place.

Those terms are rather vague and impeachment is a complex process, beginning in the House of Representatives and moving to the Senate where a vote is held to remove a president from office. The House requires a majority vote, while the Senate requires a two-thirds vote.

There has never been an impeachment by both the House and Senate, though some presidents have come close. In recent history, Richard Nixon resigned before he was officially impeached, leading Gerald Ford to take office in 1974. Bill Clinton was impeached by the House in 1998 but not the Senate.

Even if Trump completes his four-year term, Pence's presence will be felt in the Oval Office. Pence will act as a liaison to Congress and play a “big role” in the administration, Trump told the Wall Street Journal in an interview soon after his election.

Donald Trump stands with Mike Pence at the Republican National Convention in Cleveland, Ohio, Jul. 20, 2016. Getty