Gonzales's undoing really began as the Bush Administration began the war on terror. As White House Counsel to President Bush, Gonzales was responsible for the so-called torture memo and many of the policies that led to enemy combatants, Guantanamo bay, and calling the Geneva convention protections quaint. Democrats and Civil Libertarians were outraged when he became attorney general, but it wasn't until the Democrats took control of Congress in 2006, did the unraveling of Gonzales's tenure really begin.
Once word spread that numerous US Attorneys were asked to resign, for what looked like political advantage in voting rights cases, Democrats put the heat on the AG. Through numerous hearings, statements, and thousands of pages of internal Justice Department documents, Gonzales's credibility began to unravel. He did not appear to be forthcoming to the Congress and made statements that appeared to be contradictory to the official record. Many in Congress simply said they did not trust the attorney general.
And when former Deputy Attorney General James Comey testified to the Senate about a late night hospital room visit in 2004, that then-White House Counsel Gonzales made to the bed of an ailing Attorney General John Ashcroft, the wheels finally began to come off. Gonzales's testimony about the secret NSA surveillance program that the Administration had started in secret, was contradicted by not only Comey, but also by FBI Director Robert Mueller -- saying that, in effect, what Gonzales told the congress simply was not true.