All the mistakes, inconsistencies and lack of faith in the Attorney General won’t lead President George W Bush to sack Alberto Gonzales. For one reason, he’s the only thing standing between the White House and special prosecutors. TIME gives you three other reasons too.

If cabinet members were perishable goods, Alberto Gonzales would have passed his “sell by” date sometime last spring. Since January, when he first faced sharp questioning over the firing of U.S. Attorneys, the Attorney General has earned disastrous reviews for his inconsistent testimony and poor judgment and for appearing to place loyalty to the White House above service to the public.

By June it was hard to find a Republican willing to defend him. Now Gonzales’ dissembling testimony about a controversial domestic-spying program has raised suspicions about what he is hiding and fueled new calls for him to go.

Senate Democrats have called for a special prosecutor to investigate his activities as Attorney General, and a group of moderate House Democrats has called for the House to weigh impeachment proceedings against him.

Yet the embattled Gonzales’ grip on his job seems unshakable. Bush tossed Donald Rumsfeld last fall despite support from conservatives for the then Defense Secretary, and the President chucked Joint Chiefs Chairman Peter Pace at the first sign of Congressional resistance to his renomination. So why the extraordinary support for Gonzales in the face of a protracted meltdown at the Department of Justice (DOJ)? Here are four reasons why Bush can’t afford to let Gonzales go:

1. Gonzales is all that stands between the White House and special prosecutors. As dicey as things are for Bush right now, his advisers know that they could get much worse. In private, Democrats say that if Gonzales did step down, his replacement would be required to agree to an independent investigation of Gonzales’ tenure in order to be confirmed by the Senate.

2. A post-Gonzales DOJ would be in the hands of a nonpartisan, tough prosecutor, not a political hand. Newly appointed Deputy Attorney General Craig Morford is in line to take over until a new Attorney General could be confirmed. Morford, a 20-year veteran of the department, was brought in to investigate the botched trial of the first major federal antiterrorism case after 9/11. He is in the mold of James Comey, the former Deputy Attorney General who stood up to the White House over its domestic-eavesdropping program.

3. If Gonzales goes, the White House fears that other losses will follow. Top Bush advisers argue that Democrats are after scalps and would not stop at Gonzales. Congressional judiciary committees have already subpoenaed Harriet Miers and Karl Rove in the firings of U.S. Attorneys last year.

4. Nobody at the White House wants the legal bills and headaches that come with being a target of investigations.