Don't get too carried away with the poll showing that only 21% of the public identifies as Republican. Party identification is actually fairly fluid outside of a core group of partisans, and the out-of-power party almost always scores lower marks when there isn't an election on the horizons. It's certainly possible that Republican self-identification has dropped without the large media presence of the once popular Bush or the atypical Republican McCain, but a single poll shouldn't be treated as convincing evidence on that front.
Update: Okay, two polls. Well, we'll see.