Staring down the DC press corps on Sunday (May 1), Democratic presidential candidate Bernie Sanders vowed to make Hillary Clinton’s path to the party’s presidential nomination as challenging as possible. “It is virtually impossible for secretary Clinton to reach a majority of convention delegates by June 14 with pledged delegates alone,” Sanders explained to reporters at a National Press Club conference. “In other words, the convention will be a contested contest.”

While Sanders has every right to pursue the Democratic nomination until the last delegate has been counted, the odds are emphatically against him. While Sanders supporters may cling to a few theoretical strands of hope, it is all-but-mathematically-impossible for Sanders to catch up to frontrunner Hillary Clinton at this stage in the process. Heading into today’s Indiana primary, she leads Sanders 1,645 to 1,318 among pledged delegates and 520 to 39 among superdelegates. With a total of 2,383 delegates needed to secure the nomination, Clinton is in the homestretch.

Assuming Clinton is the nominee and Donald Trump—who currently leads the Republican field by a wide margin—is her challenger, there is no question who Sanders should support. While a few political commentators (and presumably Sanders fans) have suggested otherwise, the fact is Clinton’s political goals are far more aligned with Sanders than those of any candidate on the GOP side. In light of this reality, it’s time to start thinking seriously about what Sanders can do—or, for that matter, should do—to ensure a liberal (and yes, Bernie Bros, Clinton is a liberal) makes it into the White House in November. If history serves as a reliable guide, two steps come immediately to mind:

1. Select the issues that are central to the Sanders platform and hold Clinton accountable to them.

If you’re a Sanders supporter, you should actually feel pretty good about this primary season. Even if your candidate does not win the nomination, he has put himself in an excellent position to influence Clinton’s policy agenda. After all, Sanders’ campaign was never meant to be about the desires of one man. Instead, the Vermont senator’s stated goal from the beginning was to raise the national profile of issues that he and his supporters believe are important: opposition to “disastrous trade policies,” a $15 minimum wage, a carbon tax to curb global warming, stronger stances against fracking, universal health care, tuition-free college, and breaking up Wall Street’s big banks.

Clinton will need Sanders supporters to help her win the general election, but they also need her.

Regardless of how well Clinton does in the coming months, Sanders’ campaign has shone a spotlight on the millions of American voters who believe the economic and cultural status quo simply isn’t good enough. Clinton has already been pushed to the political left in part because of Sanders’ supporters. Now she will need them to help her win the general election, but they also need her if they hope to accomplish any of their original socioeconomic goals. In theory, this has all the makings of a symbiotic, if not necessarily loving, relationship. Remember, Sanders supporters have leverage—just because they elect her once doesn’t mean they’ll back her re-election bid.

Of course, this strategy will only work if the Sanders supporters fully back Clinton in this election—and that is the point Sanders must eventually make. If Clinton wins without the support of the Sanders movement, they will lose their influence. And then there’s the possibility that she could wind up losing as a result if the Democratic party remains divided heading into the national contest. This brings us to the second point:

2. Sanders needs to remind supporters of the historical consequences of putting ideological pride over common sense.

This point was perhaps best summed up by former vice president Hubert Humphrey in his memoirs, published in 1976. “Some liberals feel the only way you can be truly liberal is to take a position that cannot possibly succeed, and then go down fighting with flags flying,” Humphrey explained. “With that view, you are never so happy as when you are unhappy, and you’re never quite so unhappy as when you succeed.”

If the Sanders movement is motivated by a desire to help the less fortunate, they won’t allow pride to overshadow the bigger picture.

Humphrey understood this tendency all too well. As Democratic presidential candidate in 1968, Humphrey struggled to unify his party. This was in large part due to the fact that one of his primary opponents, left-wing senator Eugene McCarthy, refused to endorse him in anything but the most tepid fashion. The ’68 election was incredibly close, with only a razor thin popular vote margin separating Humphrey from the winner, former vice president Richard Nixon. It’s not unreasonable to assume that Humphrey could have won had McCarthy’s supporters swallowed their pride and fully supported his ticket. Similarly—in an example millennials know all too well—if Green Party candidate Ralph Nader had dropped out of the 2000 presidential election 32 years later, exit polls indicate that Al Gore may have been able to best George W. Bush in the electoral college.

While these examples may seem like ancient history to 2016’s younger voters, both occurred during Sanders’ own lifetime, and he has good reason to heed their implicit warnings. Although leftists in both elections argued there was little separation between the Democratic and Republican nominees, the administrations of Nixon and Bush resulted in resoundingly negative outcomes for the American people. It doesn’t take a political scientist to predict a similar situation if Trump is elected, beginning with the open Supreme Court seat.

If the Sanders movement is motivated by a genuine desire to help the less fortunate, they will not allow their pride or frustration to overshadow the bigger picture. My hunch is that many of the more strident Sanders supporters, though currently livid at the prospect of supporting Clinton, will ultimately do the right thing on November 8th. Sanders has a moral responsibility to emphasize both the opportunities afforded by a Clinton administration and the dire consequences of a Trump one.

While he may not be ready to admit it, Sanders actually holds more cards than he has had this entire election cycle. After energizing the electorate and pushing Clinton to defend her progressive credentials, Sanders could cement his legacy as an effective and courageous crusader against inequality. But if he refuses to heed the warnings of history—or waits to make his move until it is too late—he will be remembered as yet another shortsighted spoiler from an intransigent left.