This post originally appeared at The Nation.

Joe Biden understands something about the Democratic Party and its future that his fellow partisans would do well to consider. “I don’t think any Democrat’s ever won saying, ‘We can’t think that big — we ought to really downsize here because it’s not realistic,’” the vice president told The New York Times in April. “C’mon man, this is the Democratic Party! I’m not part of the party that says, ‘Well, we can’t do it.’” Mocking Hillary Clinton’s criticism of Bernie Sanders for proposing bold reforms, Biden dismissed the politics of lowered expectations. “I like the idea of saying, ‘We can do much more,’ because we can,” he declared, leading the Times to observe that, while Biden wasn’t making an endorsement, “He’ll take Mr. Sanders’s aspirational approach over Mrs. Clinton’s caution any day.”

Unwittingly or not, Biden made an even better case than Sanders has for taking his insurgent campaign all the way to the Democratic convention in Philadelphia. If the party is going to run in 2016 on a “do much more” agenda — as opposed to triangulating around the center — the Vermont senator’s supporters and like-minded Democrats, including Clinton’s progressive backers, will have to force the issue. Taking the Sanders insurgency to the convention is the paramount vehicle for placing demands that are ideological and, as Biden’s comments suggest, also strategic. That’s one reason why Sanders promised in a statement on April 26 to go to the convention with “as many delegates as possible to fight for a progressive party platform” — despite the fact that Clinton’s delegate advantage now all but guarantees that she will win the nomination.

Conventions are where we come together, but you don’t really come together if you avoid differences. — Rev. Jesse Jackson

What Sanders is proposing is a necessary quest — and a realistic one. Already, he is better positioned than any recent insurgent challenger to engage in rules and platform debates, as well as in dialogues about everything from the vice-presidential nomination to the character of the fall campaign. As veteran political analyst Rhodes Cook noted in a survey prepared for The Atlantic, by mid-April, Sanders had exceeded the overall vote totals and percentages of Howard Dean in 2004, Jesse Jackson in 1988, Gary Hart in 1984 and Ted Kennedy in 1980, among others. (While Barack Obama’s 2008 challenge to Clinton began as something of an insurgency, he eventually ran with the solid support of key party leaders like Kennedy.) By the time the District of Columbia votes on June 14, Sanders will have more pledged delegates than any challenger seeking to influence a national convention and its nominee since the party began to democratize its nominating process following the disastrous, boss-dominated convention of 1968.

This new reality has Clinton supporters fretting about the prospect of a chaotic convention that could expose divisions within the party when it should be uniting for what increasing looks like a fall fight against Donald Trump. But a muscular appearance by Sanders and his delegates at the convention doesn’t have to lead to bitterness. Historically, contested conventions — not carefully choreographed coronations — have led parties and their nominees to take more audacious positions and to excite broader electoral coalitions.

“Conventions are where we come together, but you don’t really come together if you avoid differences,” says the Rev. Jesse Jackson, who has protested, attended or spoken at nearly a dozen Democratic national conventions (and who has not endorsed a candidate in the primary race this year). “You start by understanding that it takes two wings to fly. If you have two strong wings — a wing that has won and a wing that has lost — you don’t deny the differences; you recognize them. You debate, find common ground, find ways to start working together for immediate goals — the next election — and for long-term goals that can mean as much to the nation as to the party.”

Contested conventions can open policy debates and clear the way for ‘significant political and social progress.’

Recent conventions have been so tightly scripted that it’s easy to forget that both parties have long histories of contested gatherings — sometimes with open combat over the party’s standard-bearer (as may erupt at this year’s Republican convention), but often with spirited competition over rules, platforms and the very nature of the party itself. Contested conventions can open policy debates and clear the way for “significant political and social progress,” argues Fitchburg State University professor Benjamin Railton, who has analyzed the history of conventions. With 18 state wins so far and more than 1,350 delegates, Sanders is uniquely poised to push for such progress. Since Clinton will likely arrive at the convention with a majority of the pledged delegates and a lead in the popular vote, she’ll have every right to argue, as she did in April, that “I am winning. And I’m winning because of what I stand for and what I’ve done.” Front-runners rarely invite input from insurgent challengers, and if Clinton chooses to wall Sanders off, she’ll have the upper hand in Philadelphia. In January, Democratic National Committee chair Debbie Wasserman Schultz appointed a pair of Clinton allies, Connecticut Governor Dannel Malloy and former Atlanta mayor Shirley Franklin, to head the platform committee. And an ardent Clinton supporter and noted Sanders antagonist, former congressman Barney Frank, will cochair the rules committee.

But Clinton’s decision to adopt what was initially Sanders’s position on a host of issues, from wages to climate change to trade policy, shows that her campaign recognizes that a substantial portion of the party’s base — as well as its potential base — is attracted to Sanders’s more aspirational message. And the pressure to make that recognition a part of the Democratic platform will grow as the committees expand before the convention and Sanders aides urge the DNC to deliver on the promise made by spokesman Luis Miranda: that the party is “committed to an open, inclusive and representative process” for drawing up the platform, and that “both of our campaigns will be represented on the drafting committee.”

If Sanders advocates gain sufficient representation to provoke debates, what are the likely pressure points? Like Jackson and his supporters, who forced rules reforms and the diversification of the DNC in 1988, the Sanders camp could champion a more open and representative Democratic Party. There could be calls for reducing or eliminating the role of superdelegates, for a better approach to scheduling debates and for consistent primary rules to avoid dramatic variations in turnout based on whether the primary is open or closed. Even though Sanders ran well in caucuses, his backers could gain credibility by also arguing that caucuses are too incoherently organized and difficult to participate in to be justified. On all of these issues, Sanders supporters would have to establish alliances with Clinton backers who recognize that it is time to “democratize the Democratic Party.”

The prospect of aligning with Clinton supporters, especially progressive members of Congress and labor activists who will attend the convention as superdelegates, creates even greater openings for platform fights. Prospective nominees tend to favor weaker platforms; Harry Truman would have preferred milder civil-rights commitments than were made in his party’s 1948 platform, and it took steady pressure from unions, liberals and Ted Kennedy to get Jimmy Carter to finally embrace spending on jobs programs. It will take similar pressure to get Clinton and her inner circle to accept a Democratic platform that Sanders says must include “a $15-an-hour minimum wage, an end to our disastrous trade policies, a Medicare-for-all health-care system, breaking up Wall Street financial institutions, ending fracking in our country, making public colleges and universities tuition-free, and passing a carbon tax so we can effectively address the planetary crisis of climate change.” Clinton stalwarts may want to keep things vague, but look for the Sanders team to demand specifics, such as an explicit endorsement of a national $15 minimum wage instead of the $12 proposal that Clinton initially offered, and an unequivocal rejection of the Trans-Pacific Partnership trade deal that President Obama supports and that Clinton once championed but now criticizes.

As it happens, many of Clinton’s most passionate allies have been outspoken supporters of the fight for $15, fair-trade policies and proposals to break up the big banks. One of them, Ohio Senator Sherrod Brown, a potential vice-presidential pick, has argued publicly that Clinton “should work with [Sanders] on the platform” in order to strengthen the party’s appeal. Other Clinton backers like Connecticut Representative Rosa DeLauro (D-CT) and nonaligned House members like Wisconsin’s Mark Pocan could play a critical role in steering the party toward unequivocal opposition to the TPP. There could also be room for cooperation on addressing mass incarceration, passing constitutional amendments to get big money out of politics and guaranteeing voting rights for all.

Sanders backers want to win these platforms fights — not to make a point about their campaign, but to make a deeper point about what the Democratic Party must stand for in order to win the 2016 election and the future. “The convention can amplify what this campaign made visible — that there are millions of Americans who are hurting — and say that the Democratic Party has to respond to that pain with bigger and bolder policies,” says Working Families Party national director Dan Cantor, a veteran of the 1988 Jackson campaign who is now a Sanders backer. “Democrats who want to win a big majority in November, to take back the Congress and to move forward in the states, know that the party has to stand for something that excites young people, that excites working people. No matter who the nominee is, the party has to take a big-vision stand.”