Real simple. If Bush decides to pull the U.S. military out of Iraq he has admitted that the Iraq War, the single signature policy of his Presidency, it an utter failure. Here is TPM's discussion of the matter.
Short answer - we all know that Bush is the President who committed the worst foreign policy decision ever done by a U.S. President. But as long as he doesn't admit it (meaning pull the troops out) he doesn't have to face his failure. He would rather have American troops and Iraqis die or be cruelly wounded and maimed rather than face his own failure.
This is the response Democrats who met with Bush to discuss his reaction to the ISG report. From the McClatchy Washington Bureau.
"I just didn't feel there today, the president in his words or his demeanor, that he is going to do anything right away to change things drastically," Senate Majority Leader-elect Harry Reid, D-Nev., said following the Oval Office meeting. "He is tepid in what he talks about doing. Someone has to get the message to this man that there have to be significant changes."Bush is severely in denial, and is resisting being pushed with every technique a life spent avoiding things that didn't fit what he wanted has taught him. My opinion? This situation could well lead to a Constitutional crisis and/or Bush's suicide. Or both.
Instead, Bush began his talk by comparing himself to President Harry S Truman, who launched the Truman Doctrine to fight communism, got bogged down in the Korean War and left office unpopular.
Bush said that "in years to come they realized he was right and then his doctrine became the standard for America," recalled Senate Majority Whip-elect Richard Durbin, D-Ill. "He's trying to position himself in history and to justify those who continue to stand by him, saying sometimes if you're right you're unpopular, and be prepared for criticism."
Durbin said he challenged Bush's analogy, reminding him that Truman had the NATO alliance behind him and negotiated with his enemies at the United Nations. Durbin said that's what the Iraq Study Group is recommending that Bush do now - work more with allies and negotiate with adversaries on Iraq.
Bush, Durbin said, "reacted very strongly. He got very animated in his response" and emphasized that he is "the commander in chief."
Bush had a friendlier afternoon meeting with leaders from the Blue Dog Coalition, a group of 44 conservative House Democrats united primarily on fiscal conservatism. Bush apparently was feeling them out to see if their political agenda could dovetail with his. But even they stressed that they expect to see him revamp Iraq policy.
"Obviously, he was most passionate in defending his position on Iraq," said Rep. Mike Ross, D-Ark. "But we made it clear to him that the American people are ready for a new direction in Iraq. I think he's open to that. Maybe not all 79, but I think you'll see some of the recommendations from the Iraq Study Group implemented in the coming months."
Bush has been cool to some of the report's main recommendations. He's said he won't deal with Iran until it verifiably suspends its nuclear enrichment program and won't sit down with Syria until it stays out of Lebanon's political affairs and prevents the flow of weapons and cash to insurgents in Iraq.
And Bush has stressed many times that U.S. troops will stay in Iraq until they successfully complete their mission.