For all practical purposes, is an ideology defined by its historical intellectual principles (otherwise its largely stagnant), or by the beliefs of the majority of people that claim to be its adherents (otherwise its largely dynamic).
For example, you constantly hear conservative ideologues (and to a slightly lesser extent liberal ideologues) claim that the policies advocated and enacted by current Republicans and conservative media pundits do not represent "true conservatism" or in the case of liberalism "true liberalism". In my opinion, conservatism for all practical purposes is what the majority of its current adherents believe it is, just like liberalism for all practical purposes is what the majority of its current adherents believe it is and thus both ideologies are fairly dynamic.
For example, when a conservative tells a liberal that Obama is a hard core liberal, that liberal might respond with "Obama is not a liberal, Franklin D. Roosevelt was a liberal, Obama is not nearly as liberal as he is." The problem with that argument is that it assumes that liberalism is a static philosophy that never changes. However, for all practical purposes even though Obama is not nearly as liberal in terms of an activist government as FDR was, Obama represents the left of center in American political discourse, thus Obama is a liberal.
Similarly, when a liberal tells a conservative that Bush was a solid right winger, the conservative might respond with "Bush is not a conservative, Barry Goldwater was a conservative, and Bush is nothing like him (or go into some Russell Kirk diatribe). The problem with that argument is that once again it assumes that conservatism is a static philosophy that never changes. Goldwater would not be a conservative today, he would be a right-libertarian. For all practical purposes, Bush represented the right of center in American political discourse, thus Bush is a conservative.
What do others think?