Now consider this: The weighted poll sample has only 23% Republican self-identification, against 39% Democrats. Even the unweighted sample is only 26% Republicans to 35% Democrats. And it's not a coincidence that that number of Republicans and the disapproval of Obama are about the same -- the disapproval starts with a majority of Republicans, with the difference made up by the minority of independents who disapprove.
As for the GOP's own numbers, they aren't good. Only 31% have a favorable opinion of the party, with 58% disapproval. By contrast, the Democrats are at 56%-34%.
For this poll, and for Pew, it doesn't look like polarization -- a word that often implies a more even divide -- so much as there are two intertwined stories: Obama's high popularity, and the GOP's heavy unpopularity. Also, any high-profile politician will have a built-in base of people who disapprove every time under normal circumstances. In this case, it's a pretty small base at the moment.