Look at Clinton’s weakness in open primaries, where independents could cross over and vote, Devine said. Those same voters would hand the election to Donald Trump in November.

“I said on that phone call that I thought Hillary Clinton was a weak candidate in the general election,” he told Fortune. “And then I was lambasted for the next two weeks. Called a misogynist and everything else because they said I was calling a woman a weak candidate.”

Trump won Wisconsin, Michigan, and New Hampshire. Every state Devine had flagged.

A decade later, he’s written a book about it, called How the Democrats Screwed Bernie, out July 7. But his argument isn’t really about Bernie Sanders at all. It’s about power, who holds it inside the Democratic Party, how they protect it, and what it costs the party when voters are cut out of the equation.

The machine

Devine said it’s now undisputed that the Democratic National Committee was actively coordinating with the Clinton campaign to stop Sanders. Leaked DNC emails that surfaced during the 2016 convention confirmed what the Sanders campaign had been alleging for months: that the party apparatus, nominally neutral, was running interference for Clinton. The DNC has not yet responded to Fortune’s request for comment.

Devine looked at Nevada, where Sanders had momentum coming off New Hampshire and was threatening to make the state competitive. Harry Reid, then the Senate Democratic leader, intervened.

“John Ralston, who was probably the best and most objective observer of Nevada politics, wrote a piece in USA Today about what happened in Nevada during the caucuses and put Hillary’s victory at the foot of Harry Reid and a deliberate effort on the part of the establishment to make that happen,” Devine said, adding Clinton’s win in the state was inevitable due to interference.

Before any votes were cast, Clinton had locked up nearly all of the party’s 800 superdelegates, who represented roughly 40% of the votes needed to clinch the nomination. “The Clinton message almost from the night that she won the Iowa caucuses—49.9 to 49.6—was her inevitability,” he recalled. “And the bedrock of it was the superdelegates.”

After the 2016 election, the DNC reformed the superdelegate system. Devine said that was a start, “but we got a long way to the finish line.”

The main crux of his thesis depends on the open primaries where independent voters could swing elections, not closed Democratic primaries. In Wisconsin, Michigan, and New Hampshire in 2016, independents flooded the Democratic primary to vote for Sanders. But in November, those same voters, faced with a Clinton-Trump matchup, went to Trump.

“Those tests are the most valid test of political strength,” Devine said. “I would argue it’s as valid, or perhaps even more valid, than polling because when you have millions of people voting in primaries, that’s a better test of political strength than 1,000 people who made it into a poll.”

When asked about 2020, Devine doubled down on the American voters’ disinterest in the status quo. “It tells me that the voters in 2020 were looking for something different than they were looking for in 2016,” he said. “In 2016, they were not looking for an establishment figure like Joe Biden or Hillary Clinton.”

What he saw in 2016, and subsequently in not only 2020 but also 2024, Devine said, is what prompted him to write the book in the first place.

“Those mistakes have been repeated cycle after cycle, with two catastrophic defeats in the recent past and who knows how many more to come in the future. If ever there was a time for me to write a book about Bernie Sanders’s 2016 primary campaign, and how the establishment crushed it, that time is now.”

It’s playing out in New York City

Fast forward to 2025: Zohran Mamdani won the Democratic mayoral primary in New York City as a self-described democratic socialist who ran on housing, public transit, and taxing the wealthy, against Andrew Cuomo, who had the institutional support, the name recognition, the donor network, and a Trump endorsement that did nothing to dampen the enthusiasm of the party’s establishment wing.

Still, despite Mamdani’s win, Devine argued what played out on the national level with Sanders and Clinton in 2016 also exists in New York.

“I think New York State is a great example of this. These are places where the limitations within the primary structure, keeping people out of participating in primaries,” Devine said, adding that “It happened to an extraordinary degree in 2016.”

While the city’s 2025 mayoral election saw the highest turnout in over a decade, he explained that a person who would otherwise want to vote in an election may not be able to thanks to how voter registration rules—which Devine said benefit the establishment—are laid out.

“People who were not registered to vote really had to get registered as a Democrat,” he said, “well late in the year before any television ad was ever broadcasted.”

New York requires eligible voters to register at least 25 days before Election Day, but the NYACLU found that this disenfranchises young voters the most. Should same-day registration have been in place during the 2016 election, more than 70,000 New Yorkers would have been eligible to vote.

But even if the rules are eased, there’s still the electability issue when it comes to democratic socialists, especially outside New York.

Devine acknowledged that a democratic socialist winning a closed Democratic primary and then a general election in the five boroughs is a different animal than winning a presidential primary in South Carolina. But unlike Sanders, the difference with Mamdani is the New York City mayor doesn’t flinch at the word Democrat.

“Bernie would never say ‘I’m a Democrat.’ Those words would not come out of his mouth,” Devine said. “Mamdani, in one of his early interviews, when they said, ‘Are you a Democrat?’ said, ‘Yes, I’m a Democrat.’ He’s not troubled by that association. And I think when we have someone like that who will embrace the Democratic Party, even though they may have a different political orientation. That’s great for the Democratic Party.”

Overall, Devine said Sanders’ message is more important now than ever. The economy has only grown more unequal, just as the campaign finance system has only grown more entrenched.

“What Bernie laid out as a central frame is true, as true or even more true today,” he said. “America has a rigged economy, which is held in place by a corrupt system of campaign finance. Someone who grabs hold of that message and runs with it will touch the hearts and minds of the American people all across this nation.”

Rules working against them

Devine argued the rules—nomination rules for presidential candidates; campaign finance rules for non-establishment candidates, and voter registration rules for would-be voters—are intentionally complex so only those with establishment backing can navigate them.

“They know that the people who are already there, who put them in power, will be there again, and they want to keep out people who may be different and have a different agenda,” he added.

Instead, the party needs to exercise tolerance from within and recognize that some people that the party must bring in will not agree with it on some issues, according to Devine.

“Let’s have a process that listens to voters,” he said, “instead of a process that tries to dictate the outcome to voters. If we adopt that as a principle, I believe we will start winning elections all over the place.”