Much ink has been spilled over the divides within the Democratic Party. Fault lines seem to be everywhere: between the college educated and the working class, between white voters and those from minority ethnic groups, between moderates and progressives, between the young and the old.

But a study released this past fall shows that there is another important divide between Democratic voters that has not received nearly as much attention.

For the study, published in The Journal of Politics, five academics researched the impact of authoritarianism on the 2016 Democratic Party presidential primaries. While much research has been done on how authoritarianism affects Republican voting patterns, this is the first detailed examination of such a trend among Democrats.

The Journal used three different data sets: the 2016 Cooperative Congressional Election Study University of Mississippi module, a YouGov study conducted in the Fall of 2017, and a sample of undergraduate students from five southern universities.

University of Mississippi political scientist Julie Wronski, one of the researchers who conducted the study, explained in an email to TAC how they defined authoritarianism. “We define authoritarianism as an individual’s psychological preferences for social conformity over individual autonomy,” she wrote. “Here we see its features as two-fold: 1) preferences for traditionalism and maintaining the conventional, established norms; and 2) preferences for maintaining group cohesion and sameness. As my co-authors and I note in the article: ‘authoritarianism is grounded in the desire to be part of a group, not in the identification with a particular social or political group.’”

In order to gauge the level of authoritarianism among voters, Wronski and her fellow researchers looked at the “child-rearing” measure, a common metric used by political scientists to quantify how much a person embraces authoritarianism based on whether they value independent or obedient traits in children.

What the researchers found is that authoritarianism consistently predicted differences in primary votes, specifically Clinton votes over Sanders votes. This remained the case as controls for a wide range of factors were included, such as party identification strength, ideology, church attendance, gender, race, education, and income.

As a voter in the “CCES sample moves from the minimum value on the authoritarianism scale to the maximum value, the probability of voting for Clinton increases from 0.33 to 0.76 while holding other influential factors constant,” the researchers noted. Results were similar in the YouGov sample and the student sample, the latter of which was even more dramatic—“the probability of voting Clinton increases dramatically from 0.18 to 0.867 as young Democrats shift from the lower end of authoritarianism to its maximum value.”

To give you an idea how important this result is, Wronski told me that “neither race nor age had a significant effect on voting for Clinton over Sanders.” However, “in one of the three studies we conducted for this article, income was significant and had a bigger effect than authoritarianism—in the direction where wealthier people were more likely to vote for Clinton.”

Perhaps surprisingly, the researchers found that the divide over authoritarianism among Democratic voters was unique to the party. While they noted that Republican voters were significantly more authoritarian than Democrats, the variation in authoritarianism was also significantly higher between Democrats than between Republicans. They even found that “the difference between Clinton and Sanders supporters is larger than the difference between Republicans and Democrats.” A similar authoritarianism divide between supporters of Texas Republican Senator Ted Cruz and President Trump was not found in any of their samples. They concluded that the “intraparty distribution of authoritarianism is largely unique to the Democratic Party.”

The researchers are less conclusive as to why Clinton was more likely to attract authoritarian voters than Sanders. “If we think about the group in this instance as the Democratic Party, it would make sense for Democrats higher in authoritarianism to gravitate to Hillary Clinton—she is a more traditional, conventional candidate, and with her decades-long career in the Democratic Party she is the established prototype of the party,” Wronski said. “Contrast her profile to that of Bernie Sanders, who adopted the Democratic Party label for the 2016 campaign and distinguished himself as a non-traditional ‘democratic socialist.’ When one thinks about authoritarianism as the need to preserve group order and establishment—regardless of the ideological leanings and policy positions of the group—then we can observe the effects of authoritarian preferences outside of the right-wing context.”

In 2016, I covered the Democratic National Convention as a reporter at The Intercept. I noticed a distinct personality difference between Clinton and Sanders delegates, one that could very well have been an indicator of that authoritarianism divide. The Clinton delegates viewed the event as an opportunity to promote the party’s eventual nominee while the Sanders delegates used it more as a protest to raise the issues that mattered to them in order to impact the party line.

For instance, the speeches of both former CIA director Leon Panetta and retired General John Allen—both of whom spoke in favor of Clinton’s national security credentials—were interrupted by anti-war chants from Sanders delegates. But they were quickly drowned out by cries of “U.S.A.,” apparently from Clinton delegates. The facility even turned off its lights on a section of Oregon Sanders delegates who continued to chant (they responded by holding up their smartphones to produce their own illumination).

It is likely that this divide will continue to persist inside the Democratic Party, particularly going into a 2020 field that will likely tackle issues along the authoritarian-libertarian divide, such as American war policy, police and prison reform, and immigration.

In 2016, Sanders’ campaign lagged behind in developing detailed plans on most of those issues; the candidate was clearly focused on economic policy.

That started to change in 2017, as Sanders branched out to lead on a wider set of issues. Importantly, he hired foreign affairs-focused progressive Matt Duss, formerly the president of the Foundation for Middle East Peace and an ex-colleague of mine, as his top foreign policy advisor. He has been outspoken on Israel’s treatment of the Palestinians, and given speeches about combating the rise of global authoritarianism. He has introduced comprehensive legislation to seek to end the national usage of cash bail.

Unlike in 2016, Sanders would enter the 2020 presidential race as one of the frontrunners should he choose to be a candidate. The question is whether he would once again tap into that anti-authoritarian sentiment among likely Democratic voters.

The 2020 presidential field is likely to be far bigger than the 2016 one, and the role Clinton played as a steady establishment hand with more hawkish and religious credentials than her opponent could be played by any number of prominent Democrats, including former vice president Joe Biden, who is leading in many of the primary polls.

Unlike Sanders, Biden has been squarely on the more traditionalist side of the Democratic Party. He was one of the architects of the Clinton-era tough on crime policy, and once boasted in a speech that “every time Richard Nixon, when he was running in 1972, would say ‘law and order,’ the Democratic match or response was ‘law and order with justice,’ whatever that meant. And I would say, ‘Lock the SOBs up.’’”

Other potential contenders have staked out more hawkish positions than Sanders. New Jersey Democrat Cory Booker co-sponsored the Anti-Israel Boycott Act, which would punish those who choose to boycott Israel or its settlements over its treatment of the Palestinians. California Democrat Kamala Harris gave an off-the-record speech to the American Israel Public Affairs Committee, America’s powerful pro-Israel lobby.

How authoritarian (or not) will Harris and Booker end up sounding? We’ll have to wait until 2020 to know for sure. But one thing is certain: the Democratic Party is split and the usual dichotomies can’t fully explain what’s going on.

Zaid Jilani is a contributor to The Intercept.