There were two wide divides separating the two leading Democratic candidates in the party’s 2016 primary fight. Young voters overwhelmingly supported Sen. Bernie Sanders (I-Vt.). Black voters overwhelmingly preferred Hillary Clinton.

In the Iowa caucuses that year, the latter split wasn’t really a factor, given the state’s demographics. But the difference in support by age wound up offering a remarkable way of viewing the results, which were essentially a tie.

Entrance polls conducted by Edison Media Research for the National Election Pool, The Washington Post and other media organizations showed a massive 75-point lead for Sanders among caucus-goers under 25. As caucus-goers got older, that gap narrowed. Once caucus-goers were over the age of 40, Clinton had an advantage. Among the oldest caucus-goers, Clinton had a 43-point advantage of her own.

The reason the contest ended up close is that those older caucus-goers made up much more of the pool of people who turned out — 28 percent — than the youngest cohort, who made up only a tenth of those who attended a caucus.

One of the reasons that Sanders is faring as well as he is in the 2020 contest is that he’s maintained a steady core of support from the outset. That core largely matches the support he enjoyed early in the 2016 primaries as well, before he benefited from swelling support as the sole viable opponent to Clinton.

On Monday, Iowa held its caucuses. The results, while still hazy around the edges, were similar to four years ago: Sanders and former South Bend, Ind., mayor Pete Buttigieg are essentially tied. Digging into the numbers, though, things look a bit different. (Note that these are preliminary results from a survey of voters as they entered randomly selected caucus sites on Monday. The results have a margin of sampling error of plus or minus four percentage points.)

Sanders still holds a lead among younger caucus-goers, but a more modest one than he did four years ago. The only age group where he has a majority — or where any candidate has a majority — is among 25- to 29-year-olds. Sanders’s plurality dissolves once you hit that 40-to-49 age group, where Buttigieg earns the most support.

Former vice president Joe Biden has the most support among the oldest caucus-goers, earning a third of their support. Four years ago, Sanders won about a quarter of this group. This year, he has earned only 4 percent of it.

It’s also worth noting how Sen. Amy Klobuchar (D-Minn.) and entrepreneur Andrew Yang fare. Klobuchar, like Biden, earns more support as the age of caucus-goers increases. Yang does much better with younger caucus-goers, earning very little support among older ones. If you compare Yang’s support to Sanders, you notice that among those under 25 or those 30 to 39, Sanders’s support fades a bit and Yang’s increases. The aforementioned margins of error are worth remembering here; this may just be noise.

More interesting is how the peak of Sanders’s support has shifted one age cohort older. His most fervent supporters in the Iowa entrance poll are those aged 25 to 29, people who were aged 21 to 25 four years ago — and, therefore, in that youngest group of caucus-goers. Sanders’s supporters are getting older, as are we all. The youngest Iowans considering who they would vote for this year, though, were more likely to consider a non-Sanders option (like Yang or Buttigieg) than those slightly older.

If we sort the candidates into two broad groups of support — Sanders, Sen. Elizabeth Warren (D-Mass.) and Yang versus Buttigieg, Biden and Klobuchar — something else stands out relative to 2016.

The more moderate second group fares better than Clinton did against Sanders alone four years ago. Biden, Buttigieg and Klobuchar have the support of about a quarter of the youngest voters, a group with which Clinton could manage only 11 percent.

Why has Sanders emerged with the most support in the first round of the caucuses and, at least for now, the final tally? Because more of those younger caucus-goers came out to participate. A quarter of those who attended the caucuses were under the age of 30, compared with a fifth of the 2016 attendees. Had that been Sanders’s strongest group, as it was four years ago, there would be little question about the results of the caucuses.