Historians will no doubt mark last night's Indiana primary as a watershed moment in American politics. Imagine, one year ago, suggesting to a random selection of pundits and elected officials that Donald Trump would, on May 3, 2016, become the presumptive nominee of the Republican Party. On asking them for a written response to that proposition, you would have received a stack of essays that, whatever their stylistic and thematic differences, concurred in framing the notion as insane. Today the world is a different place.
This restructuring of fundamental laws, moreover, applies on both sides of the aisle. In the old world, the natural course for the second-place candidate in the Democratic nominating contest would be to close ranks with the front runner and form a unified front for the upcoming general election. This is, in fact, what Hillary Clinton did during the race of 2008, when despite having won more votes and only 4% fewer pledged delegates, she conceded the contest to Barack Obama and formally nominated him on the floor of the Democratic convention.
Those who view the current race through the prism of the old rules will no doubt expect Bernie Sanders, given world enough and time, to behave in the same way as the Hillary Clinton of 2008. They will be sorely disappointed. To understand why this is so it is useful to imagine an alternative past. What would have happened if, in 2008, Hillary had persisted in framing the nominating process as a "contested contest"? She could have forced the superdelegates at the 2008 convention to choose between herself and Barack Obama, and perhaps even wrested the nomination from him. She refrained from that course because it would have fractured the Democratic coalition and, whether she succeeded in seizing the nomination or not, thrown the election to the Republicans. In the long run, forcing a contested convention would have foreclosed Clinton's future in Democratic elected politics.
Sanders is operating under none of the constraints of Clinton circa 2008. He does not worry about his future in Democratic elected politics because, by the old rules, he should not have a present in Democratic elected politics. If one year ago you had told the same random group of pundits that, at this point, an avowed socialist would hold more than 40% of the delegates to the Democratic convention, the written response would have been comparable in tone to that produced by the Trump exercise. Sanders has consistently sought the nomination of the Democratic party in the service of an economic populist agenda, and anyone who is waiting for him to compromise his agenda in service of the party's electoral hopes will wait in vain.
Moreover, anyone who believes that Sanders's constituency is frivolous or ephemeral in their support, ready to rally behind Clinton in the face of a Trump candidacy, is likewise self-delusional. Free trade agreements, wage stagnation, the erosion of organized labor, infrastructural decay, and a shrinking public sector have debilitated large swaths of the American public, leaving them feeling angry at and betrayed by the entire political system. Their support of Bernie Sanders has been given in clear understanding of and approval for his agenda, and if he breaks ranks with the Democrats they will follow him, or throw their support to Donald Trump, who is offering different solutions to similar problems.
Sanders has it in his power to scuttle the election for the Democrats, and he will use it if they do not bend to accommodate his agenda. What, then, should the Democrats give him? Short of the nomination, anything he wants.
The situation of the Democratic party exemplifies the shibboleth about "crisis" and "opportunity" being synonymous in Chinese. A wrong move at this point will hand the country over to the tender mercies of Donald Trump. But the Democrats still have a chance, that the GOP has forfeited, to capitalize upon this historic moment. By nominating Donald Trump the Republicans have forgone the opportunity to forge a new electoral coalition in favor of a malignantly nativist politics that has no long-term future. By contrast, if the Democrats can compromise and cooperate, they stand the chance of bringing constituencies back into the fold that have been abandoning the Democratic party since the days of Ronald Reagan. A new progressive politics could be on the horizon. It only awaits Clinton and Sanders to meet the test of leadership.