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In the United States the President of the United States may involuntarily be removed from office through impeachment.
This is outlined in Article 2 of the United States Constitution
The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.
This is to protect the president from unwonted prosecution and to allow for he or she to execute the office with minimal distraction or fear that their actions will be personally litigated at every turn. The president is still liable in federal court once their term of presidency is over but not during.
That said...is the prohibition against removing the president only extended to those crimes committed while in office or would they also include crimes committed in an effort to gain the presidency?
Edit: As a point of clarification I know the 25th amendment also provides for the involuntary removal of the president if he/she is deemed unable to execute the office. I am specifically looking for removal due to crimes committed prior to becoming president and the impeachment process.
Edit 2: As clarification I am looking for instances, case law, or references that would indicate the Congress can bring Articles of Impeachment for crimes committed prior to the individual actually taking office.
This article from http://history.house.gov/Institution/Origins-Development/Impeachment/ outlines the previous uses in the federal government but each one was used based on infractions taken by the individual while in office
The Use of Impeachment
The House has initiated impeachment proceedings more than 60 times but less than a third have led to full impeachments. Just eight—all federal judges—have been convicted and removed from office by the Senate. Outside of the 15 federal judges impeached by the House, two Presidents (Andrew Johnson in 1868 and William Jefferson (Bill) Clinton in 1998), a cabinet secretary (William Belknap in 1876), and a U.S. Senator (William Blount of North Carolina in 1797) have also been impeached.
Blount’s impeachment trial—the first ever conducted—established the principle that Members of Congress and Senators were not “Civil Officers” under the Constitution, and accordingly, they could only be removed from office by a two-thirds vote for expulsion by their respective chambers. Blount, who had been accused of instigating an insurrection of American Indians to further British interests in Florida, was not convicted, but the Senate did expel him. Other impeachments have featured judges taking the bench when drunk or profiting from their position. The trial of President Johnson, however, focused on whether the President could remove cabinet officers without obtaining Congress’s approval. Johnson’s acquittal firmly set the precedent—debated from the beginning of the nation—that the President may remove appointees even if they required Senate confirmation to hold office.