Tuesday night's Democratic primary in the District of Columbia brought the 2016 presidential delegate selection season to an official end, four and a half months after it began with the Iowa caucuses. While Hillary Clinton has accumulated enough delegates to win the Democratic nomination, her opponent Bernie Sanders remains—for now—an active presidential candidate. At some date in the near future, Sanders will no longer be a candidate and will instead be a supporter of the Clinton campaign. The precise sequence by which Sanders moves from A to B is presumably the main topic of discussion at a private meeting between Clinton and Sanders that occurred in Washington Tuesday evening.
It is clear that Sanders intends to use his current status as an active rival candidate to extract concessions from Clinton and, by extension, the Democratic National Committee. Clinton supporters frustrated at Sanders's behavior might object that their own candidate, in a similar position eight years ago, dropped out of the race at the end of the primaries and immediately endorsed the victorious Barack Obama without apparent conditions. Yet Clinton did receive something quite valuable in exchange for her unequivocal support of Obama in June 2008: credentials as a loyal Democrat and team player that not only gave her the opportunity to hold a high-level position in the Obama administration, but also allowed her to position herself as Obama's (tacitly-sanctioned) successor in the presidential office once he reached the constitutionally-prescribed two-term limit.
Sanders has a different set of interests. His age prevents him from being a realistic candidate in 2024 or even 2020, and his independence makes him a poor fit for a position in somebody else's presidential administration. Instead, he has three other objectives in mind: (1) winning demonstrable influence over the Democratic platform in order to be able to boast to his supporters that they succeeded in pulling the party to the ideological left; (2) forcing reforms to the presidential nomination process, both as another achievement to claim for his campaign and as a procedural benefit to future insurgent candidacies; and (3) visiting revenge upon DNC chairwoman Debbie Wasserman Schultz, whom Sanders blames for exhibiting a perceived favoritism toward the Clinton campaign during the nomination process.
This is an ambitious wish list for a losing presidential candidate to expect from the winner, and it seems unlikely that Sanders will be in a position to insist upon all of his demands. Indeed, his leverage over Clinton is quickly beginning to weaken—in part because of the identity of the presumptive Republican nominee.
The looming nomination of Donald Trump undercuts Sanders's bargaining position in three ways. First, Trump's routine dominance of the daily political news directs attention away from the Democratic race, making it more difficult for Sanders to win the publicity he needs to press his case. Second, Trump is something of a custom-built Democrat repellant, which will encourage even Clinton-wary Democratic voters to rally quickly around her as the only person standing between their archnemesis and the White House even if Sanders himself remains a holdout. Third, Clinton and her advisors likely view Trump as eminently beatable whether or not they receive Sanders's blessing, which makes them more likely to call Sanders's bluff than if they were facing a race against Marco Rubio or John Kasich.
Given Sanders's rapidly eroding strategic position, here's my best guess for how the Clinton-Sanders contest gets resolved:
(1) Sanders will soon suspend his campaign and make a public gesture of support for Clinton—though he might save a wholehearted endorsement until the convention itself.
(2) With Clinton's support, Sanders will win approval of platform language echoing his anti-Wall Street campaign message.
(3) The Democratic convention will approve a resolution calling for an internal party commission to study potential "democratizing" reforms to the presidential nomination process prior to the 2020 elections. It is less likely that the resolution will commit to specific reform provisions sought by Sanders such as requiring open primaries or abolishing superdelegates.
(4) Wasserman Schultz will stay at the DNC through November.