The Pew Research Center for the People and the Press is a polling organization with, if anything, a leftward bias. Their work is frequently reported on PBS's News Hour. In data reported out on April 2, Pew
finds:
Barack Obama has the most polarized early job approval ratings of any president in the past four decades (emphasis added). The 61-point partisan gap in opinions about Obama's job performance is the result of a combination of high Democratic ratings for the president -- 88% job approval among Democrats -- and relatively low approval ratings among Republicans (27%).
And Pew concludes:
The growing partisan divide in presidential approval ratings is part of a long-term trend.
Since it is "part of a long-term trend," it cannot realistically be ascribed to racism.