http://nymag.com/daily/intelligencer/2016/04/pragmatic-tradition-of-black-voters.html
The Democratic primary is a reprise of the classic purity-versus-pragmatism conflicts that periodically break out in both parties. Purists (on the left and the right) cast voting in morally absolute terms. They believe a hidden majority of the electorate shares their preferences, and a sufficiently committed, eloquent, or uncorrupted leader could activate that majority. Sanders is a classic proponent of this worldview. He has portrayed conservatism as simply a false consciousness constructed by big money and a biased news media, and something that would, in an uncorrupted system, be reduced to 10 percent of the public or less. Pragmatists read the electorate much more pessimistically. They recognize that the other side votes, too, and, having lowered expectations of what is possible in the face of a divided country, recognize that progress will be incremental and weighed down by compromise — sometimes with truly odious forces. That is the history of even the most spectacular episodes of progress in American history. Abraham Lincoln, who was holding together a coalition of voters that included supporters of slavery, refused to support abolition until the very end. Franklin Roosevelt needed the votes of southern white supremacists, and had to design social programs to exclude southern black people in order to pass them through Congress.
No community in the United States is more aware of the power of its enemies than African-Americans.
And pragmatism inflects the African-American view of how politicians perform in office. Purists see compromise as a sign of moral failure or weakness, an inability to smash a corrupted system. Pragmatists expect political opposition as normal and enduring. A politician who has their best interests in mind and pushes policy in the proper direction is better than the all-too-common alternative. Sanders’s campaign draws much of its strength from the left-wing critique of Barack Obama’s presidency, which it dismisses as largely feeble half-measures. Sanders has attracted Democrats most discontented with Obama’s progress, while Clinton wins those most satisfied, among whom African-Americans are disproportionately represented. Obviously, Obama’s status as the first black president creates a unique bond with black supporters, but much more than racial affinity is at work here.
But the critique of Clinton’s African-American supporters increasingly lies outside the realm of calculation altogether. Columnist Shaun King, a Sanders supporter, argues that “Political progressives across this country, in supporting the candidacy of Bernie Sanders, are completely rejecting the Democratic Party,” and should take their actions a step farther and “form our own political party.” Similar logic animates online activists declaring themselves for “Bernie or Bust.” Any drawn-out primary will produce overheated declarations of refusal to support the opposing candidate. But it is not surprising that many of Sanders’s most prominent supporters, like Susan Sarandon, Cornel West, and Michael Moore, not to mention Sanders himself, endorsed Ralph Nader in 2000. (Nader in 2000 drew the support of 3 percent of whites, but just one percent of African-Americans.)
That refusal to accept the necessity of compromise in a winner-take-all two-party system (and an electorate where conservatives still outnumber liberals) is characteristic of a certain idealistic style of left-wing politics. Its conception of voting as an act of performative virtue has largely confined itself to white left-wing politics, because it is at odds with the political tradition of a community that has always viewed political compromise as a practical necessity. The expectation that a politician should agree with you on everything is the ultimate expression of privilege.