Could liberals do better than Obama in 2012?

Sen. Bernie Sanders, I-Vt., thinks one result of this debt-ceiling fiasco should be a 2012 primary challenge for President Obama. But the Daily Beast’s Eric Alterman observes that “as angry as many liberals may be — and I count myself among them — the fear engendered by the craziness of the current Republican crop of candidates provides a strong corrective to any dreams of mounting anything more than a nuisance candidacy to challenge Obama. . . . Barack Obama is not going to be seriously challenged from his left any more than he is going to be impeached.”