As far as I know this has never happened before: the right-hand aide of the highest-ranking cabinet member--the Secretary of State--calling for the impeachment of the president who appointed his boss:
Powell's Chief of Staff Proposes Impeachment | AfterDowningStreet.org: By David Swanson: On Thursday, May 10, 2007, Lawrence Wilkerson, speaking on National Public Radio, proposed impeaching President George W. Bush and Vice President Dick Cheney.... Wilkerson is a Retired Army Colonel, the former Chief of Staff at the State Department from 2002 to 2005 under then Secretary of State Colin Powell, a Vietnam War veteran, the former Acting Director of the Marine Corps War College at Quantico, and currently a teacher of national security at William and Mary College.
The program, On Point, was hosted by Tom Ashbrook, who focused the discussion on a need for greater public accountability for the Iraq War, but who maintained that the public was not outraged or interested. (Ashbrook should read some polls and invite on organizers of the impeachment movement.) Also on the program was Ken Adelman, who promoted the war and said it would be "a cakewalk". Adelman argued a case for not holding public officials accountable. Wilkerson said in early comments on the show: "This administration doesn't know how to effect accountability in my opinion." But he did not raise the possibility of impeachment until after a member of the audience had phoned in.
The first caller who was put on the air demanded an investigation of the lies that launched the war, and asked for accountability "all the way up." In response to Adelman's claims that history would hold people accountable, the caller said "I would love to have a job where, worst case scenario, my historical record is flawed." Ashbrook framed the question in terms of alleged limitations of the U.S. political system, and Wilkerson replied: "Well I do think that that's a reality of our system. However, let me back up just a minute and say that I really do think that our founding fathers, Hamilton, Washington, Monroe, Madison, would all be astounded that over the course of our short history as a country, 200 plus years, we haven't used that little two to three lines in Article II of the Constitution more frequently, the impeachment clause. I do believe that they would have thought had they been asked by you or whomever at the time of the Constitutional Convention in Philadelphia 'Do you think this will be exercised?' they would have said 'Of course it will, every generation they'll have to throw some bastard out'. That's a form of accountability too. It's ultimate accountability."
After an interruption, Wilkerson continued: "The language in that article, the language in those two or three lines about impeachment is nice and precise – it's high crimes and misdemeanors. You compare Bill Clinton's peccadilloes for which he was impeached to George Bush's high crimes and misdemeanors or Dick Cheney's high crimes and misdemeanors, and I think they pale in significance." Ashbrook asked for some examples of such high crimes and misdemeanors, and Wilkerson replied: "I think that the caller was right. I think we went into this war for specious reasons. I think we went into this war not too much unlike the way we went into the Spanish American War with the Hearst press essentially goading the American people and the leadership into war. That was a different time in a different culture, in a different America. We're in a very different place today and I think we essentially got goaded into the war through some of the same means."