More moderate Republicans and Independents that still support Bush with many reservations are still hanging on to him, like the last thread in a frayed rope, because he is "tough and can handle international terrorism". This misguided idea assumes that he is somehow wrongheaded on the economy, the environment, etc, but knows what he's doing on the War on Terror. In reality, he's just as disastrous there for two good reasons:
One: Responding with the macho instinctive approach to 9/11 with a display of force might have been effective if we had been wholly successful. And then it might not have really inspired fear and respect among people that think more like Palestinian suicide bombers than rational Westerners. Unfortunately, this move carried huge risk. If our ploy failed, then we look weak and our military power is tied up and unable to be deployed against threats elsewhere. There is no doubt that we have not succeeded enough to have the needed effect of engendering fear in the enemy. As time goes on, it remains to be seen if this makes us look just as weak as the Soviets did in Afghanistan - or whether it will turn out to be a major strategic mistake when our forces are needed to fight a real threat and are unavailable. A huge risky gamble that will not necessarily pay off. Does this seem like a good strategy - or the actions of deluded old men drunk with the power of having access to the full military power of the US.
Two: The Bush administration has let OBL win in many ways. By responding to terror with fear, weakening the freedoms necessary to keep our society an open democracy, OBL is indeed destroying America, turning our beloved country into something less than it was before. We are so frightened of losing our lives to terrorism, that we are willing to lose our lives to fear. Rather than saying "We are strong, you can't really hurt us with attacks like this. America is still the land of dreams and freedom." - a renewed version of "We have nothing to fear but fear itself", the Bush administration breeds an environment of fear, using this fear to justify the altering of our political and social institutions to increase the power of government and move the country inexorably towards fascism.