Because he's black?

Harold Meyerson: Obama won't face a primary challenge because he's black.

The other reason Obama hasn’t faced a challenge, and isn’t likely to, is that he’s black. Any Democrat who would challenge Obama, whatever the basis of his or her candidacy, would almost surely encounter intense opposition from the party’s African American base, the one group in Democrats’ orbit that regularly votes Democratic at a 90 percent rate. Such a challenge could create a rift that might take decades to heal.

Should have figured Meyerson was projecting when he accused Hillary Clinton of racism.

Needless to say, this is not why Obama has no primary challenger. For all his faults Obama is an effective and strategic politician. He neutralized his most effective Democratic opponents, has taken great care to de-fund any potential alternate liberal power centers, and passed health care reform. As economists pointed out early on his economic policies were inadequate, his failure to spur economic recovery is the one major threat to his re-election. But he was never at risk of being primaried.

UPDATE: Now Eleanor Clift is making the same claim in the Daily Beast.

Anyone contemplating a run against Obama must consider the consequences of not only defeating the president, but the likely repercussions to his or her own career. “If he were white, he would have a progressive challenger,” says Bill Schneider of the Democratic group Third Way.

Clift and Schneider appear to have forgotten 1996, when a president with poor poll numbers, who just lost the House, and who was white, had no serious primary challenger.