These are highly partisan times in America. "Bipartisanship" (or, in the Obama nomenclature, "post-partisanship") makes for a catchy campaign slogan, but is difficult to execute upon in practice. The White House's aspirations (or pretense) of running a bipartisan administration died a quick and ugly death with two events: firstly, the House Republicans' decision to whip votes against Obama's stimulus package so as to produce a unanimous nay vote, and secondly, the Administration's decision to try and kneecap Rush Limbaugh.
Nonetheless, measurements of the partisan split in support for the President, as Pew Research has done here (they found a record partisan split in Obama's approval ratings, with 88 percent of Democrats but just 27 percent of Republicans approving of Obama's performance) are not quite as straightforward as they might seem. This is because partisan identification is at least somewhat fluid. The Republicans, in particular, have lost quite a bit of support over the past several years; those persons who continue to identify as Republicans are a hardened -- and very conservative -- lot. Just 24 percent of voters identified as Republican when Pew conducted this survey in March, which is roughly as low as that total has ever gotten.
We see some evidence of these effects in the comparison of Obama's numbers to those of George W. Bush's at a comparable point in his presidency. Obama and Bush had roughly the same level of support among members of their own party (88 percent for Obama, 87 percent for Bush) and roughly the same level of support among unaffiliated voters (57 percent for Obama, 56 for Bush). Bush, however, had more support from the opposition party (36 percent of Democrats versus 27 percent of Republicans). And yet Obama, not Bush, had the higher overall approval rating, because Democrats are a significantly larger constituency than Republicans.
A more telling measure might be to see a breakdown in support by voters who identify themselves as conservative, moderate or liberal. These categories are somewhat fluid too -- but less so than partisan ID.