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Hillary Clinton and Bernie Sanders are now in an extended process of negotiating the terms of his surrender. But I’m beginning to wonder if Sanders understands just how few cards he has left to play.

Yesterday, the DNC announced the makeup of the committee that will decide the party’s platform, with Clinton choosing six members, Sanders choosing five, and party chair Debbie Wasserman Schultz choosing four. Clinton chose the kind of people you might expect, covering bases with the party’s key constituencies — a union leader, a prominent Latino congressman, the chief of a liberal think tank — while Sanders picked mostly activists who could be considered outsiders (although his inclusion of Cornel West, among the harshest African-American critics of President Obama, could be seen as a rather curious middle finger to the Democratic Party’s leader and most popular figure).

So now that’s settled, and even if the committee has some spirited arguments, most Democrats, not to mention most Americans, aren’t going to be all that concerned with what’s in the platform, an almost entirely symbolic document. We can ask what else Bernie Sanders wants, and the answer is less than clear. He’d obviously like to influence Clinton’s eventual presidency, with input on appointments and policy choices. The problem is that at this point, he has almost nothing left to bargain with.

We tend to talk in vague terms about things like “unity,” so it’s helpful to get as specific as we can. Sanders can no longer beat Clinton. So let’s say he feels that he’s not getting what he wants out of this negotiation. What can he do to force her to be more accommodating to him? There are really only two things:

  1. Cause some kind of disruption at the convention, which will look bad for Clinton.
  2. Tell his supporters not to vote for her.

And that’s it. Is he actually willing to do either of those things? Just this morning, his campaign is explaining away his offhand comment yesterday that the convention could be “messy,” making clear that he wasn’t trying to issue a threat, just saying that there will be vigorous debates. So he doesn’t seem to have any appetite to recreate the 1968 Chicago convention. And would he tell his supporters not to vote for Clinton? That wouldn’t just be the final card he could play, it would also be the end of any hope he’d have at retaining influence in the future. If Sanders did that, he’d be done as a political force in American politics.

Why do I say that? Sanders may have been a political independent throughout his career, but now that he’s playing at a much higher level than he used to, any influence he has is going to have to come within the Democratic Party. And if he tells people not to vote for the Democratic nominee, he will have banished himself. To Democrats everywhere, he’ll be the guy who tried to get Donald Trump elected because Hillary Clinton wasn’t nice enough to him. If Trump actually won, Sanders would be Ralph Nader times 100, without even the remotest bit of plausibility Nader had in denying that he was responsible for George W. Bush winning the White House in 2000. And if Clinton won even after Sanders tried to destroy her, he’d have zero chance of having his requests considered by the White House mail room intern, let alone the president. He’d also gain the eternal antipathy of his Democratic colleagues in the Senate.

It’s also important to understand that if Sanders tried to convince his supporters to reject Clinton, it almost certainly wouldn’t work. Yes, there would still be a few of the “Bernie or Bust!” folks we see on the news, but they’re a small and shrinking fringe even among Sanders supporters. Once the general election is underway, almost everyone who voted for Sanders will see the election not through a frame pitting Hillary Clinton against Bernie Sanders, but through a frame pitting Hillary Clinton against Donald Trump. In that context, not voting for her will take on a very different meaning.

We know this, because we’ve seen it before. This isn’t the first contested primary in American history. If you look back over previous elections, what you see is that contested primaries don’t produce large-scale defections in the general election. Here’s a chart showing the proportion of crossover votes — Democrats voting Republican and Republicans voting Democrat:

What we see here, first, is that Democratic loyalty increased as conservative Southern Democrats switched parties and became Republicans, a process that started with the civil rights efforts of the Johnson administration and was essentially complete by the time we got to the 2000s. But more importantly, we see large-scale defections in either party not because of something that happened in primaries, but because of what’s going on in the general election, usually when there’s a blowout, like many Republicans voting for Johnson in 1964 or Democrats voting for Nixon in 1972. And the most recent era of the last four elections is characterized by unwavering partisanship, with at least nine out of ten partisans sticking with their party, no matter what happened in the primaries.

So if Sanders tried to get his supporters to turn against Clinton, he’d probably fail. And at this point, anything he does that makes life more difficult for Clinton will likely hurt him more than her.

Let’s think back to 2008, when not only did Clinton get behind Barack Obama after a primary race that ended on much more bitter terms than this one, she did so in a public, dramatic way. When the delegates were formally presenting their votes in a roll call on the convention floor, they arranged it so that New York’s votes would put Obama past 50 percent of the delegates. Standing amidst her state’s delegates on the floor, Clinton made a motion to suspend the roll call vote and declare her former opponent the party’s nominee by acclamation, to the rapturous cheers of the crowd.

As a piece of political theater, it was pure genius. It sent a signal of unity to Democratic voters, making her voters feel better about supporting him and his voters feel better about her. And in the process, it helped ensure Hillary Clinton’s future in the Democratic Party. It told everyone that she was a team player, that she wasn’t consumed by resentment, and that she’d be enthusiastically supporting the party’s champion and, everyone hoped, the next president. Had she gone off in a huff and given sullen interviews to the press about how she really deserved to be the nominee, it’s a good bet that Obama wouldn’t have named her Secretary of State, and she wouldn’t be where she is now.

Will Sanders do something like that? I have no idea. But he surely understands that he’s in a difficult position, and he has a great deal to lose if he doesn’t play this right. If he were to actually try to get his supporters not to back Clinton, even they would realize that it would be for nothing but spite — not a more liberal party, not policy concessions (because by doing that he’d give up any chance of achieving those things), but just spite. So he can’t plausibly threaten to walk away from this strange negotiation. He can make his case for two more weeks until the last big primary day. Then he’ll have to find a way to take whatever Clinton is willing to give him and get behind her — and at least pretend that he’s happy about it.