So let's take a Braudelian view: the most important decisions are made for a leader by history, the Reagan era arms buildup started under Carter, and the collapse of the Soviet Union was caused by Saudi Arabian oil production, which removed the petrodollar support for the socialist economy. No matter who is elected President, he will probably have to stay in Iraq for a while, will have to deal with Iran, will have to contain North Korea, will preside over migrational waves into the United States from Central America and from Asia. Presidents have to deal with inevitable, glacial historical forces, but their method of dealing with them can make a difference, if only because they can accelerate or delay different events. So it is quiet plausible that Reagan accelerated the collapse of the Soviet Union by a few years, and those years meant a lot to the people under its tyranny (especially in Poland and the Ukraine).
So the question is not whether McCain or Obama is not fundamentally unsuited to be President -- history will guide both of them to make remarkably similar decisions -- the question is which one of them will be a better vessel for the Zeitgeist. And Obama is clearly in better physical shape, the challenges of the presidency will require, above all, stamina.
