Tyler Cowen has column in the New York Times suggesting that the scope for Presidential elections making a whole lot of difference with respect to economic policy is relatively modest:
To put it simply, the public this year will probably not vote itself into a much better or even much different economic policy. To be sure, the next president — whoever he or she may be — may well extend health care coverage to more Americans. But most of the country’s economic problems won’t be solved at the voting booth. It is already too late to stop an economic downturn.
Of course, it is impossible to know the true effect of an election on economic policy because it impossible to observe the counterfactual state of the world --what would have happened if the other person was elected. I think in this respect, the November 2000 election, however, is something close to a natural experiment because it was so close. The difference between Bush and Gore was basically a coin toss. More accurately it was the difference of a butterfly ballot, a thousand Nader votes or one Supreme Court Justice.
The fact that it was close suggests that we are essentially holding constant the pre-election preferences of the electorate, i.e. the popular vote was actually higher for the candidate who was not in favor of the large tax cuts that actually took place. In that sense the closeness of the election addresses the problem that the preferences of the electorate are "endogenous" (in econ speak) with the outcome of economic policy post-election.
So imagine that all else was the same but the butterfly ballot was properly designed, Gore won Florida and became President instead of Bush.
Here's the question, do you seriously believe that we would have pursued the same economic policies, that the value of the our national debt would be the same today as it would have been under Gore? Too me it strains credulity to think so. Gore likely would not have slashed tax rates at the top, entered the war in Iraq and signed a joke of a Prescription drug bill. Would Gore have reacted the same way to the prolonged jobless recovery? Certainly not. One might argue that the housing bubble and the credit crunch likely would have ensued under a Gore administration, maybe so, but Gore would not have had the same people in charge of the key banking and regulatory agencies that took pride in being completely hands off.
In fact, once you start to think about it more broadly the US and the world likely may very well have been on a completely different trajectory. Now this is admittedly much more speculative but 9/11 might not have even happened if there was a continuation of the predator program in Afghanistan or if the Gore Administration reacted the same way to the August 6th memo as Clinton did to the threat of a millenium attack.
So does it really matter if McCain or Obama (or Hillary) are President? ...I think so, just think of McCain singing "bomb, bomb Iran".
(Note post was updated to try to more clearly explain the argument)