Skepticism on Ds vs. Rs

This post by Brian Caplan makes some great points about the lack of any substantive differences between the two parties. This certainly matches my experience.

For example, if you ask republicans why they supported McCain over Obama, they often cite differences that are not even real. Both support middle class tax cuts, both want to stop global warming, both are in favor of missile defense, both want to increase the size of the Army and Marine Corps, both favor restrictions on late term abortions, etc.

Similary, differences between Bush and Kerry were often more in emphasis than substance. In particular, thinking back to the start of the Iraq war, Kerry argued that it is critical to gain the support of allies (multi-lateralism), but admitted that the president must ultimately do what is in the interests of the American people. Bush argued that it was most important to do what is in the interests of the American people, but admitted that it is better to have as much support from allies as possible. What's the difference between those positions? Emphasis.

Of course, it is well known that candidates "run to the center" during an election. This is predicted by the median voter theorem as well as common sense. However, to win, the candidate must also get his base to turn out, and that usually requires convincing those voters of important substantive differences between themselves and their opponent.

How can a candidate do this while actually taking extremely similar positions? Rhetoric. The easiest rhetorical tactic is for him to ascribe to his opponent views that he does not actually hold, and then argue against those (which really are different) instead. This is called the "strawman" argument. And this is leads to Rs and Ds often having substantial misconceptions about the views of their candidate's opponent, like the ones mentioned above held by republicans about Obama.