In an excellent post, Greg Mankiw laid out why it doesn't make sense to judge a president's economic policy the way most of us do now:
"Even the best physicians have patients die. And even witchdoctors can have patients recover...Randomness is a fact of economic life, and it would be a mistake to judge a president by the economic outcome during his administration. It is better to look at the decisions the president made, and to acknowledge that the outcome is a function of those decisions and many other factors not under his control. As an economist, I have views about what best practices are for economic policy, and I judge presidents by how closely they adhere to those principles. "Often, events on the macroeconomic scale are too difficult to disentangle from one another. It's very easy to judge a president by the economy during his time in office. However, the impact of the president on our economy is a lot smaller than most people think. Mankiw makes a strong case for gauging a presidents actions in an intelligent manner, instead of a simple one.