A 2016 article in Psychology Today explored whether having a mental illness would make it difficult for a candidate to get elected president. The author, Guy Winch, Ph.D., cited a study by Jonathan Davidson of Duke University Medical Center that found that of the first 37 U.S. presidents, "half of those men had been afflicted by mental illness — and 27% met those criteria while in office, something that could have clearly affected their ability to perform their jobs."

The study found that 24% of presidents met the diagnostic criteria for depression, including James Madison, John Quincy Adams, Franklin Pierce, Abraham Lincoln, and Calvin Coolidge.

Davidson and his team also found evidence of anxiety disorders, bipolar disorder and alcohol dependence among sitting presidents.

Although the 25th Amendment to the U.S. Constitution can prevent an incompetent president from remaining in office, the amendment was not created specifically for that purpose.

The 25th Amendment addresses what happens to the presidency and vice presidency if the president and/or vice president dies, resigns or becomes incapacitated or disabled.

About two years after the assassination of former President John F. Kennedy, Congress recommended a succession amendment. On Feb. 23, 1967, former President Lyndon B. Johnson, Kennedy's successor, who, by the way, may have suffered from bipolar disorder, signed the 25th Amendment into law.

Imagine in 1867 or 1967 if the president made a profane-laced statement in reference to Iran that "a whole civilization will die tonight," or a president who frequently naps at meetings took on the Pope as "WEAK on crime, and terrible for Foreign Policy." Is an 80-year-old, at times rambling, president with — as noted by The Hill — dark, unexplained bruising spanning the back of both hands — appropriate for the 25th Amendment consideration?

Succession has been a problem since the infancy of America. The original Constitution allowed for the vice president to become acting president if the president died.

That wasn't good enough for John Tyler who became "Vice President Acting President" in 1841 when former President William Henry Harrison became the first president to die in office. Tyler moved into the White House and assumed full presidential powers, including giving an Inaugural Address.

The first few sections of the 25th Amendment are straightforward. First, if the president dies or resigns — think Richard Nixon — the vice president takes over. Second, if the vice president dies or resigns — think Spiro Agnew — the president appoints a replacement approved by Congress.

Section 4 of the 25th Amendment is a little trickier.

Whenever the vice president and a majority of either the principal officers of the executive departments or of such other body as Congress may by law provide, transmit to the president pro tempore of the Senate and the speaker of the House of Representatives their written declaration that the president is unable to discharge the powers and duties of his office, the vice president shall immediately assume the powers and duties of the office as acting president.

Section 4 of the 25th Amendment has never been used, although officials considered invoking the section after the 1981 assassination attempt on Reagan.

However, like impeachment or indictment, the president has Due Process rights. The president can challenge the declaration of incapacity. If he or she does, the vice president and other administration officials must reassert the claims or the president resumes his authority.

If the claim is reasserted, Congress must decide the issue. Within 21 days of assembling, Congress must vote with a two-thirds majority of both houses that the president is unable to fulfill his constitutional responsibilities as president.

If the two-thirds super-majority is not met in both houses of Congress, "the president shall resume the powers and duties of his office."

For now, there is little chance of invoking the 25th Amendment. The President is Republican, the House is Republican, the Senate is Republican and the Vice-President is a sycophant. There are other options — the midterms are just months away ... a dramatic power shift is not out of the question.

Matthew T. Mangino is of counsel with Luxenberg, Garbett, Kelly & George P.C. His book, "The Executioner's Toll," 2010, was released by McFarland Publishing. You can reach him at www.mattmangino.com and follow him on Twitter @MatthewTMangino

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