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A specter is haunting the Democratic Party—the specter of socialism. 
For several years, this hard-left movement has been gaining support within the party, especially among younger voters. In a few deep blue districts, socialist/populist candidates like Alexandria Ocasio-Cortez and the Squad have managed to defeat entrenched center-left incumbents. The movement is now powerful enough that House Speaker Nancy Pelosi chose to press forward with impeachment, which she never favored, to retain her leadership position. Bernie is pressing an equally radical agenda in the primaries. He finished in the top two in Iowa and is currently leading a weak field in next week’s New Hampshire primary.
Party leaders are appalled—and alarmed—by Sanders’ strength. They uniformly opposed him in 2016, and they are doing exactly the same this year. They favor Biden, Klobuchar, Buttigieg, Bloomberg, or even Warren—anybody but Bernie.
When party insiders “feel the Bern,” it’s acid reflux. Democratic donors, lobbyists, think tanks, and elected officials are convinced their party is doomed this November if an avowed socialist heads the ticket. They’re right, but they don’t have an easy answer.
The insiders’ dilemma is simple to state but tricky to solve. They think Bernie’s nomination would be an electoral disaster, but they must prevent it without alienating his supporters. They need them to win in November.  
As the party’s standard bearer, Bernie would be George McGovern reincarnated. He would not only cost Democrats the White House, he would cost them close races for House and Senate seats. Every Republican would force his Democratic opponent to say if she supported this avowed socialist and his costly, transformational policies. That’s why party pros want to stop Bernie before it’s too late. So does every Democratic candidate outside Berkeley and Ann Arbor.
Their challenge is to do it without estranging Bernie’s ardent followers. The harder insiders work to block Bernie, the less chance they have of keeping Bernie’s people in the General Election. Those voters may not cross over to Trump (although about one in 11 did in 2016), but they could stay home. 
Bernie himself would be incandescent with rage if party insiders blocked him. He would direct that fury at the party regulars who sunk him, including the nominee. That’s exactly what he did in 2016, when Hillary actually won more primary votes but also rigged the process with her cronies at the Democratic National Committee. 
Bernie was livid at the time --- and would be now if he didn't think he had lost fairly. Actually. He will probably think he was robbed no matter what. Along side other happy losers, he ranks alongside Stacey Abrams, Hillary Clinton, and Vince Lombardi. The question is whether his disappointed supporters would coalesce around the eventual nominee, especially a centrist one. That’s still an open question. The party’s best answer would be a strong, charismatic alternative. Right now, they simply don’t have one.  
If the primaries end in a dumpster fire instead of a cozy hearth, the Trump campaign will start fracking intensively underneath the flames. The president will tell every rally how Bernie was cheated. His goal would be less to capture Bernie’s voters than to paint the Democratic nominee as yet another Swamp creature. Doing so would reinforce his central message: the system is rigged by Washington insiders for their own power and profit. Since Democrats are the party of government, they fit the picture nicely. Naturally, Trump will say he is determined to fight them and win. 
The Democrats’ dilemma evaporates if Bernie loses the nomination, but only if his supporters believe he lost in a fair fight. That certainly could happen. But it might not. The Democratic field is not especially strong. Gone are the halcyon days when the party congratulated itself on its diverse field. Now, the leading candidates are three old white guys and one young one, this in a party built on identity politics. Biden has held steady at about 30% of primary voters—a remarkable achievement, given the Republicans’ continuing assaults and Biden’s own staggering ineptitude. Still, he hasn’t moved up and is far short of dominating the race. He finished near the bottom in Iowa and could collapse entirely in later contests.
The Democrats’ nominating process increases the likelihood of a contested convention—and a nasty fight with Bernie and his supporters. The party discarded the traditional, Anglo-American system, where each state’s winner receives all its delegates. Instead, they chose a European-style system in which each candidate wins a fraction of the delegates proportional to his share of the vote. The Anglo-American system produces clear winners and losers. The European system doesn’t. It includes all factions in Parliament, where the leading party tries to assemble a governing coalition.
Democrats’ problem is that they are nottrying to form an inclusive, coalition government. They are trying to pick a nominee, but they are doing it with a system that was never designed to produce a single, decisive winner. Oops.
If the convention is contested, elected delegates will be joined by “super delegates,” starting on the first or second ballot, depending on the convention rules. Who are these super delegates? They are quintessential insiders, mostly state and local elected officials. There is absolutely no way they will jeopardize their own fiefdoms by choosing Bernie or any other socialist.
Their refusal will produce a bitter clash if Bernie arrives in Milwaukee with millions of votes and millions of donors. If he actually holds a plurality of elected delegates and is passed over anyway, the fight will degenerate into trench warfare. Remember, Bernie knows this is his last rodeo, and he has zero loyalty to the party. Remember, too, that his default speaking style is “really angry,” interspersed with “damned mad.” If that’s how Bernie and his supporters leave the convention, it’s hard to see a Democratic path to victory.
The party’s best outcome would be for Bernie to lose decisively in both the primary vote and delegate count—so decisively that his followers believe the process was fair and the nominee legitimate. A bad outcome would be an inconclusive primary contest, where Bernie did well but lost at the convention.
Worst of all would be one where Bernie arrived with the most votes and delegates but fell short of a majority and came away empty-handed. He would blame party leaders and their back-room deals to benefit billionaires, corporations, and corrupt politicians. If that happens, the party will be in real trouble. Bernie will scream, Trump will exploit the divisions, and left-wing voters will spend November 3 in a purple haze, eating Ben and Jerry’s. What they won’t do is trudge to the polls and vote Democratic.
Charles Lipson is the Peter B. Ritzma Professor of Political Science Emeritus at the University of Chicago, where he founded the Program on International Politics, Economics, and Security. He can be reached at charles.lipson@gmail.com