Main article: List of John McCain presidential campaign staff members, 2008. On July 2, 2008, Steve Schmidt was given full operational control of McCain's campaign. Schmidt had managed Arnold Schwarzenegger's 2006 re-election and was a top Dick Cheney aide.
Monopolistic competition. The model of monopolistic competition describes a common market structure in which firms have many competitors, but each one sells a slightly different product.
(In reality they may be the same good one the same demand scale.) An increase in the price of gas at one station will have a perfectly correlated effect on the increase in demand at the other station. Monopolistic competition presents an interesting case of complications with the concept of perfect substitutes.