The biggest story to come out of the Democratic caucus in Iowa, beyond Clinton’s razor-thin margin of victory, was the overwhelming generational divide within the party. So far this split has been explained by political differences over health care and income inequality within the Democratic Party, but polling suggests a similar generational divide exists over Israel and could just as much define where the party is headed.

In announcing the “The Great Democratic Age Gap” Ronald Bronstein writes in The Atlantic, “The most powerful lesson from the Iowa caucus results is that Democrats are facing not just a generation gap, but a Grand Canyon-sized chasm.” The New Yorker declared “Bernie Sanders Just Changed the Democratic Party.” What those articles are referring to is this:

84% of people aged 17-29 supported Sanders in the Iowa caucus.

14% supported Clinton, 600% less. pic.twitter.com/oKChuocavj — Ben Norton (@BenjaminNorton) February 2, 2016

The results were striking and entrance polls to the caucuses seemed to point to a clear trend: Democratic caucus goers in Iowa under the age of 45 supported Sanders, and above it supported Clinton. This is not the first time we’ve seen polls with this stark divide within the party. For the last several years we have been seeing polls showing that the Democratic base is slowly divorcing itself from Israel, and much of that dropping support is happening along generational lines as well.

In December 2014 Shibley Telhami and Katayoun Kishi wrote in the Washington Post on a recent American public opinion survey on the Israeli-Palestinian conflict. One of the trends they pointed out was the generational divide brewing within the party on the issue:

Generally, younger adults (ages 18 to 29) tend much more to want the United States to lean toward neither side. But among young Democratic respondents, the results are more striking: Among those who want the United States to lean toward one side or the other, more young people want the United States to lean toward the Palestinians than toward the Israelis (12 percent vs. 10 percent, respectively). This attitude is unique among this age group, as only 5 percent or less of Democrats in each older age group want the United States to lean toward the Palestinians.

This was also seen in the summer of 2014 while Israel was attacking Gaza. A Gallup poll taken at the time found young people and Democrats increasing saw Israel’s actions as “unjustified“:

51% of Americans 18-29 years old think the Israeli attack is unjustified. Most support from Israel comes from ages 50 and up …the majority of Republican identifiers back what Israel is doing. Meanwhile, Democrats take the opposing view, with nearly half saying Israel’s actions are unjustified.

And this is was not the first time this trend was identified. A year earlier the late Leonard Fein reported on a Pew Research Center survey for the Forward and asked, “Is Israel Losing Young Democrats?” Fein wrote,

When it comes to Americans favoring Israel over the Palestinians, Israel wins by a wide margin — 54% to 8%. Alas, if that’s as far as you read, you will be woefully underinformed. For that number is only for Americans aged 65 and older (though the next age bracket down, 50-64, is pretty much the same). In the 30-49 age bracket, Israel drops to 47%, and the Palestinians inch forward to 11%. And in the 18-29 bracket, Israel is favored by 36%, the Palestinians by 19%. This profusion of numbers can, I know, be daunting, but their gist is plain: A chasm separates Democrats and Republicans when it comes to sympathizing with Israel. And if, as some analysts believe, the Democrats’ general advantage with young people is likely to persist, that chasm may well grow.

Getting closer to the election year, last February Gallup produced several polls at the height of the controversy over Benjamin Netanyahu’s invitation to address Congress. Those polls also showed that Republican support for Israel was much stronger, with the percentage of Democrats sympathizing with Israel dropping almost 15% from the previous year, and that older Americans of both parties tended to have a more favorable view of Israel. Then, this past summer, pollster Frank Luntz made news with a survey of Democratic Party “elites” which found 47% of Democrats agreed that Israel is a racist county.

What does this mean today? It means the issues that Bernie Sanders has used to energize his young base should also include a fundamental rethinking of the U.S.-Israel relationship.

So far Sanders has stayed away from foreign policy beyond his opposition to the Iraq War. But challenging Hillary Clinton’s growing embrace of Benjamin Netanyahu offers him another opportunity to draw a progressive distinction between him and his opponent, and polling suggests that his emerging base would support him if he did. A November 2015 survey by Telhami found (PDF), “While Republicans overall have a much more favorable views of Netanyahu than unfavorable ones, Democrats have a more unfavorable view of the Israeli leader by a ratio of about two to one. In general, older Americans admire the Israeli leader far more than the younger ones.”

Back in 2014 Telhami and Kishi predicted this very moment, and the possibility that a candidate like Sanders could harness this shift in the Democratic base during the 2016 primaries,

While the Israeli-Palestinian issue is itself not so central [in Democratic primaries], it is part of a new Democratic identity and a subset of a broader human rights issue that Democrats care about. Just as with other issues that help mobilize Democratic voters, no aspiring politician can afford to look ahead to national elections by bypassing their Democratic electoral base in the primaries. If public opinion continues on its current trajectory, especially among Democrats, the Israeli-Palestinian conflict may very well play a greater role in electoral politics in the years to come.

So far it hasn’t. But all indications show that the age cohort that makes up the Sanders’s base is pulling away from Israel. The only question is whether the candidate himself will follow.