Question: Why Are Republicans Graded on a Curve?

Why are Republicans graded on a curve? Everyone in the Mainstream Media has said, "Oh, well McCain's not a good public speaker" and then said the same about Sarah Palin, basically the idea that she is inexperienced and will not do well.

Yet, when these tepid speeches are completed, why do the Media go into paroxysms about how much better they did than anyone thought? Particularly if you're a Republican, and you don't believe in quotas, or "grading on a curve", than why are McCain and Palin accorded such kudos for speeches that pale in comparison to even the worst Democratic speaker last week?

Just a question...