The question, however, is not whether there’ll be a contested convention, but rather what kind of contested convention Sanders and his supporters might produce. If we examine the history of contested conventions in prior presidential campaigns (there have been 18 total since 1868), two clear, distinct trends emerge: destructive contests that resulted in divisions between political parties; and those that contributed instead to constructive conversations and significant political and social progress.

For the worst case on the Democratic side, two 20^th century contested conventions reflected and extended the party’s ideological splintering on issues of race and culture. In 1924, Ku Klux Klan members and other white supremacists attacked the Catholic Democratic front-runner, Governor Alfred Smith of New York, leading to a convention that went through more than 103 ballots before settling on a compromise candidate, West Virginia Congressman John W. Davis. And in 1948, the entire delegations from Mississippi and Alabama (among other Southern delegates) walked out of the convention to protest the party’s addition of a civil rights plank to its platform; these delegates would help create the new Dixiecrat Party, which nominated Strom Thurmond in opposition to Democratic nominee Harry Truman.

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Both the 1924 and 1948 contested convention signaled deep ideological and social divisions, but led to debates and policies that furthered — and worsened — those divisions. If Sanders and his supporters emulate these prior conventions, whether by opposing the nomination of Hillary Clinton at all costs, walking out to form a third party, or seeking to nominate their own candidate by capitalizing on party and national divisions, these historical examples — moments of infighting and ideological extremism that pulled both party and nation apart — bode poorly for the results.

Yet a contested 2016 Democratic convention doesn’t have to follow those models, and the more constructive historical examples suggest vital alternatives. Two of the most influential 20^th century Democratic presidents, Woodrow Wilson and Franklin Delano Roosevelt, were nominated in their initial presidential campaigns at contested conventions. In 1912 the Progressive Wilson needed 46 ballots to secure the nomination against a far more conservative front-runner, Missouri Congressman Champ Clark; while in 1932 Roosevelt needed four ballots to secure it over Speaker of the House John Nance Garner and KKK favorite William Gibbs McAdoo.

In both cases, the contested conventions and the debates they produced continued in meaningful ways into the men’s presidencies: Wilson’s opposition to Tammany Hall, the conservative political machine that had endorsed Clark, helped him refine and articulate his own Progressive platform; while Roosevelt chose Garner as his VP running mate and in his convention acceptance speech promised to provide “a new deal for the American people” (the first such framing of his overarching plan to battle the Depression).

Offering even more overt models for candidates exerting influence despite suffering defeat at a contested convention are the examples of Richard Bland and Robert Pattison at the 1896 Democratic convention. Although it was the populist Senator William Jennings Bryan who was nominated on the convention’s fifth ballot, the anti-imperialist Bland and the anti-corporate Pattison both helped pull the Democratic party and its platform in significant new directions, ones that would influence the party’s opposition to President William McKinley’s imperial ventures and contribute to the rise of the Progressive movement.

It’s a separate question, of course, whether these contested conventions helped or hindered their party’s electoral chances. In truth, the results seem mixed: Truman, Hayes, Wilson, and Roosevelt won their respective elections, while Davis and Bryan lost theirs; overall, only seven of the 18 eighteen candidates nominated at contested conventions went on to win the presidency. Yet Sanders would be the first to note that the goal isn’t simply or even principally winning the 2016 election; it’s influencing both a party and a national conversation for many years to come. To achieve that end, he and his supporters can’t just angle for a contested convention—they (along with Clinton and her supporters, to be sure) have to work to make it a constructive rather than destructive conversation, one that contributes to policy debates and social progress rather than reflecting and furthering party divisions.

Ben Railton is a professor of english studies at Fitchburg State University.