Both Attorney General Alberto Gonzales and President Bush fell back on the tired, evasive, noncommittal nonapology – “mistakes were made” – as evidence mounted that the White House and the Justice Department colluded in a two-year plot to purge federal prosecutors they judged to be disloyal to the Bush administration.

Mr. Gonzales insisted that the dismissals of eight U.S. attorneys was not politically motivated. He said he would focus on what went wrong and try to correct it. Lawmakers must ensure he does not simply try to correct what the president termed the “mishandling” of the dismissals, but should review why the attorneys were fired.

What exactly were these “mistakes” that have triggered mounting outrage by lawmakers of both parties and several demands for Mr. Gonzales’ resignation? The worst mistake was committing to writing – in a series of e-mails – the two-year plan to politicize the federal prosecution system by firing U.S. attorneys deemed to be uncooperative with the political needs of the administration. From the administration’s point of view, a second mistake was letting those e-mails go public. The Justice Department surrendered them to the Congressional Judiciary Committees rather than wait for subpoenas that would have been inevitable now that Democrats are in control and can pursue their oversight role.

A first step in the two-year firing scheme came in 2005 when Republicans quietly inserted a little-noticed provision in the renewal of the Patriot Act. The provision overturned a long-standing requirement that nominations of new U.S. attorneys had to be confirmed by the Senate. The Justice Department had asked for the change so that any top prosecutor who might be assassinated by terrorists could be replaced without delay.

But the stream of e-mails show that it wasn’t terrorism but political maneuvering by the White House and the Justice Department that brought this loophole into use.

In early 2005, Harriet Miers, the White House legal counsel whom Mr. Bush tried briefly to put on the Supreme Court, proposed replacing all U.S. attorneys. D. Kyle Sampson, Mr. Gonzales’ chief of staff, countered with a list of “targets” for firing gathered from complaints that they were too easy on Democrats or too tough on Republicans or merely that they stood in the way of a Republican groomed for their job. Mr. Sampson, who since has resigned, sent the White House a five-point blueprint for carrying out the firings simultaneously without causing a political flap. The White House approved the plan and Ms. Miers sent a brief e-mail to Justice on Dec. 4 saying: “We’re a go.” Seven of the firings took place on Dec. 7, shortly before the Democrats took control of Congress.

Mr. Bush, during a stop in Mexico, said the firings were appropriate because U.S. attorneys serve at the pleasure of the president. But, he said, he did not pass on instructions to fire specific attorneys, just complaints he had heard about them from lawmakers.

This explanation is as unsatisfactory as “mistakes were made.” In an administration that values loyalty over performance, blaming the firing of the eight on poor job performance in the face of evidence of political intervention rings hollow.