Not really. If you (the hiring entity) hope for a result to be favorable for Republicans, why not hire a pollster with an R bias? This is not to accuse Gravis of fudging their numbers -- I do not at all believe they are -- but results have shown that their results tend to bias R. This is most likely due to their models and methodology. Other pollsters have D biases, and someone hoping for a D-friendly result would be more likely to hire them; for example, Democracy Corps (I just posted something similar to this in the thread about their recent poll.) Still other pollsters have little to no bias.
There's certainly a market for pollsters that are favorable to each side. Pollsters like Gravis and Democracy Corps are just filling this niche in the free market.
