A strong case can be made that President Bush is incapacitated, seriously disabled, mentally deranged, that he has a shaky grasp on reality, that he is wantonly leading the nation into a path of self-destruction. Literally, there is abundant evidence that Bush meets the diagnostic criteria for a number of serious mental disorders, and that his mental illness is so severe that it has led to a profound impairment in his judgement and in his ability to carry out his duties. Interestingly, his Vice President seems to be participating in the very same pattern of self-destructive behavior. In psychiatry, there is a term for this kind of shared psychosis or shared delusion: It's called folie a deux, or literally a folly of two.
The classic case is the two older women in the film Arsenic and Old Lace. Two seemingly normal women who are actually certifiable, who share a common set of delusions, and who behave so self-destructively that they end up committing several murders.
But how, if Bush and Cheney are found to be mentally incapacitated and harmful to others (actually, to the nation), how would they be removed from office?
Our Constitution has addressed this kind of issue, though provisions of the Constitution have only been invoked (to our knowledge) in cases of death or major surgery or serious physical illness. It's not clear whether any President has been temporarily deemed unfit for completing his duties, but there are probably some cases that we haven't read about, such as Presidents who drank themselves into a semi-comatose state for a day or two.
from Wikipedia:
The 25th amendment, ratified in 1967, clears up many of the issues which surrounded presidential succession and incapacity. Section 1 made it clear that in the event of a vacancy in the office of President, the Vice President succeeds to the office, while Section 2 established a procedure for filling Vice Presidential vacancies.
Pertinent text of the Amendment
Section 3. Whenever the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that he is unable to discharge the powers and duties of his office, and until he transmits to them a written declaration to the contrary, such powers and duties shall be discharged by the Vice President as Acting President.
Section 4. 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.
Thereafter, when the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that no inability exists, he shall resume the powers and duties of his office unless the Vice President and a majority of either the principal officers of the executive department or of such other body as Congress may by law provide, transmit within four days 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. Thereupon Congress shall decide the issue, assembling within forty-eight hours for that purpose if not in session. If the Congress, within twenty-one days after receipt of the latter written declaration, or, if Congress is not in session, within twenty-one days after Congress is required to assemble, determines by two-thirds vote of both Houses that the President is unable to discharge the powers and duties of his office, the Vice President shall continue to discharge the same as Acting President; otherwise, the President shall resume the powers and duties of his office.
Self-declared incapacity
Section 3 of the amendment set forth a procedure whereby a President who believes he will be temporarily unable to perform the duties of his office may declare himself "unable to discharge the powers and duties of his office."
Upon this declaration, which is transmitted in writing to the Speaker of the House of Representatives and the President Pro Tempore of the Senate, the Vice President becomes Acting President. The Vice President continues to act as President until the President declares, by another letter to the leaders of each house of Congress, that he's again able to discharge the powers and duties of the presidency.
Incapacity declared by Vice President and Cabinet
Section 4 of the amendment sets forth a second procedure establishing presidential incapacity. This second method allows the Vice President, together with a majority of the members of the President's cabinet, to declare the President disabled.
Upon this declaration, which is transmitted in writing to the Speaker of the House of Representatives and the President Pro Tempore of the Senate, the Vice President immediately becomes Acting President. The Vice President continues to act as President until the President declares, by another letter to the leaders of each house of Congress, that he's again able to discharge the powers and duties of the presidency. The Vice President and the cabinet may countermand that declaration, however, whereupon Congress must convene in emergency session to decide who shall discharge the powers and responsibilities of the presidency.
Ostensibly to be used in the event of a President's complete mental or physical disability, this method of transferring presidential power has never been used. In cases such as the 1981 assassination attempt on President Ronald Reagan however, this method of designating an Acting President could have been justified, in consideration of the fact that Reagan was literally unable to give any orders in the immediate aftermath of the shooting, prompting the Secretary of State to proclaim "I'm in control here."