**Must-Read:** As I see it, this is essentially the Downsian political science model applied to primaries: in order to win a primary, Republican candidates need to try to hug the center of the distribution of *primary voters*. But then once they are the candidate of the party, they seek to get as close to the median from the right as possible in order to maximize their chances of winning the general election, or winning reelection. Republican candidates striking a balance between these two will be thus governing to the right of what they promised their (very moderate) winning-margin slice of the electorate, and governing to the left of what they promised their (very partisan) primary supporters. Since you are all but guaranteed to have a general election opponent but may well not have a primary opponent, Republicans in office are under Downsian pressures to make the gap between them and the median general-election voter greater than the gap between them and the median primary voter.

Hence: disappointment

The same argument applies, of course, to Democrats and the left...

From whence asymmetry arises is, I think, a difficult and unsolved problem...

**Bruce Bartlett**: Republican Presidents Always Disappoint: "Much of the debate in Republican circles for the last several election cycles has been about how Republican presidents always disappoint...