Are white, anti-Obama liberals motivated by racism?

That’s Melissa Harris-Perry’s tendentious contention in her latest Nation column. The crux of her argument:

The 2012 election may be a test of another form of electoral racism: the tendency of white liberals to hold African-American leaders to a higher standard than their white counterparts. If old-fashioned electoral racism is the absolute unwillingness to vote for a black candidate, then liberal electoral racism is the willingness to abandon a black candidate when he is just as competent as his white predecessors…

President Obama has experienced a swift and steep decline in support among white Americans—from 61 percent in 2009 to 33 percent now. I believe much of that decline can be attributed to their disappointment that choosing a black man for president did not prove to be salvific for them or the nation.

Her proof? The Tulane political-science professor argues white liberals have been tougher on Obama than they were on the similarly centrist Bill Clinton. Welfare reform, hypertrophied federal incarceration rates, and disproportionately high black unemployment rates all occurred under Clinton—yet he was “enthusiastically reelected.” Meanwhile, the left perpetually pillories Obama for a record that’s “at the very least, comparable to that of President Clinton.”

Corey Robin recently wrote a scathing riposte to the column, noting the lack of empirical support for Harris-Perry’s provocative thesis:

According to this SeptemberWashington Post story, “Five months ago, 83 percent of African Americans held ‘strongly favorable’ views of Obama, but in a new Washington Post-ABC news poll that number has dropped to 58 percent.” That’s why, according to this piece, Obama has made special outreach efforts to blacks: he’s worried about their dwindling support. But as the Post also goes onto explain, “That drop is similar to slipping support for Obama among all groups.”

I’m more of a leftist than a liberal, so I guess Harris-Perry’s biting critique isn’t really directed at me. Regardless, I think she’s unfairly besmirching the white liberals who have deserted Obama. It’s worth underscoring that the president still receives higher approval numbers from liberals and liberal Democrats than any other ideological or ideological/partisan cohort, respectively. (Almost 70 percent of liberals support the president, as do nearly four out of five liberal Democrats.) Some segments of the left are incensed; the preponderance still offer their support, whether uncritically or begrudgingly.

Much as I hate to admit it, anti-Obama liberals comprise a small sliver of the left—quite vocal, but still a sliver. It’s activists, bloggers, and lefty journalists that are making the apoplectic din, not rank-and-file Democrats. Clinton, of course, wasn’t forced to confront a blogosphere. Save for liberal magazines and interest groups, there wasn’t a comparable online community that would assail him for his centrist ways; I have no doubt he would have been similarly scorned for his moves to the middle.

So if the Obama’s flagging support among liberals is essentially a canard, what’s going on here? Maybe Harris-Perry’s point is that the vocal left is motivated by subterranean racism. This is possible, of course, but as far as I can tell it’s not very plausible. And it certainly lacks grounding in hard empirical data. Coming from a social scientist like Harris-Perry, such uncorroborated claims are doubly startling.