The 25th Amendment has been used 3 times to relieve presidents deemed unfit to govern — each case involving physical health

President Donald Trump's inner circle is said to be facing fears that the biggest threat to his presidency is not impeachment, but rather his cabinet using the 25th Amendment to declare him "unable to discharge the powers and duties of his office."

The amendment has been invoked in this way only three times before, and coincidentally, each time has involved presidential colons.

The 25th Amendment of the Constitution was passed in 1967 after fears about presidential succession after President John F. Kennedy's assassination. The first two sections deal with presidents and vice presidents resigning, dying, or being generally removed from office, and these sections were invoked in order to elevate Gerald R. Ford to the presidency after Richard Nixon resigned in 1974.

The second two sections of the amendment deal specifically with what to do with a president who is unfit to serve, and it is these sections Trump has to worry about. If he is removed under these sections, he would be joining a small list of presidents who all had their powers temporarily removed due to doctors operating on their colons.

The first time this happened was on July 13, 1985, when President Ronald Reagan sent a letter directing then-Vice President George H.W. Bush to perform his duties while the president underwent a surgery to remove cancerous polyps from his colon. Bush was acting president from 11:28 a.m. when Reagan was given general anesthesia to 7:22 p.m. when Reagan sent another letter to members of the Senate and resumed his powers.

President George W. Bush had not one, but two instances in which he was deemed "unable" to perform the duties of the president during his two-term tenure.

The first case occurred on June 29, 2002 when he invoked the 25th Amendment and allowed Vice President Dick Cheney to act as president on his behalf for two hours and five minutes. The second one took place five years later on June 21, 2007, when Bush again named Cheney acting president for two hours and 15 minutes. In both cases, Bush, like Reagan, had undergone colon-related procedures, but his were of a much more benign nature — they were routine colonoscopies.

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