Republican Presidents have an interesting life cycle. Support, Amnesia, and Mythologizing
During their presidencies, Republicans support them unquestioningly. With Fox News creating an intellectual monolith, and central control of funding to campaigns, both political and social elements of the right-wing support their president one million percent.
Once they leave office, Republicans erase all memory of the president from the world. This is George Bush's current status. This allows the Republican groupthink to overcome the problem of an unreasonable philosophy colliding with the real world. By forgetting all the times their politics didn't work, and had to be compromised for the sake of practicality, they lay the groundwork for the next Republican platform, same as the last one.
After a few decades, Republicans fill in the missing information with ridiculous myths. This is the status of Ronald Reagan, who reduced taxes, cut government, and balanced the budget, all without hurting anyone. They've created a man who won the cold war and rescued the Iranian hostages through pure force of will. Even Nixon has undergone this, to a lesser degree. Republicans will insist that we didn't lose the Vietnam War, for example.