The new concern in the American-Jewish community is the number 25. According to a Gallup poll conducted in the midst of the Gaza war, 42 percent of all Americans supported Israel’s action. Among people aged 18 to 29, that number was 25 percent.

This set off all the usual alarm bells here and in Israel. Israel has one great and powerful ally in the world — the United States of America. But that support ultimately depends on the will of the people. And the young people — they’re not so willing.

“Israelis need to look both outward and within,” Israeli columnist Nahum Barnea wrote this week in Yediot Aharanot. “Israel is at a nadir in its foreign relations. The problem begins with public opinion in the West, including Jewish public opinion in the United States. … Israel is losing the young people.”

What’s happening is a generational shift in the quality and quantity of younger Americans’ support for Israel. Pew Research Center surveys indicate that young people still show more overall sympathy to Israelis than to Palestinians, but that number is also in decline. It’s a problem that may be easier to explain than to solve.

When it comes to Israel, there are two generations of Americans:

Generation ’67 sees Israel as a historical redemption story that began with the Holocaust, came to fruition with the War of Independence and climaxed with the Six-Day War.

Millennials see an Israel apart from Jewish history, a country among countries; 20-somethings came of age during two intifadas, the Second Lebanon War and three Gaza wars. The Israel they saw in headlines blasted homes, put up a wall, built settlements. Where Generation ’67 sees the lamb beneath the lion, millennials just see a lion.

For this generation, the arguments of Israel’s defenders clearly don’t resonate.

Devorah Brous, who works with many young people through her food-justice organization, Netiya, explained it to me this way: “The younger generation saw Gaza as an offensive war against the Palestinians, not a defensive war against Hamas.”

This despite all the fact books Generation ’67 distributes on campuses, all the exposés we send one another against the biased media, all the cool new social media initiatives. These open donors’ wallets but not young people’s hearts. It is all, to borrow Brous’ phrase, “Jewish conversation with other Jews about Jewish things.”

So, who has been successful in mobilizing a younger generation?

You’re not going to like the answer.

Jewish Voice for Peace’s (JVP) growth in popularity among Millennials is inversely proportionate to Israel’s decline. According to federal tax filings, JVP revenues went from $310,000 in 2011 to $1.1 million in 2012, and almost doubled again this year. Since Operation Protective Edge began, the organization, with 40 chapters nationwide, reports it has had 50,000 new people — Jews and non-Jews — register on its website.

JVP is a leader of the Boycott, Divestment and Sanctions (BDS) movement. Its email alerts bring Jewish and non-Jewish activists out to disrupt speeches by Israeli officials. It calls for “democratic participation and equality” for all people of the Middle East, an end to Israeli military force against Palestinians, and for Palestinians to stop attacks on Israeli civilians.

JVP uses the language of civil rights and nonviolence to garner support among Millennials. It relies heavily on social media to inform or sway its members. And it’s a Jewish group that speaks to more than just Jews.

Students are drawn to JVP because it draws a crowd that reflects the world they know. During the debate on Israel divestment at UCLA this spring, some 600 people showed up to speak for and against, and sat on opposite sides of the room.

“On one side of the aisle were mostly Jewish students and Jewish faculty members,” Estee Chandler, JVP’s regional director, told me, “and on the other side, you saw America: gay, straight, Jewish, Muslim, Christian, black.”

“Israel is no different than other social issues for the younger generation,” Chandler said. “It is about equality and justice and civil rights across the board.” Younger people, she said, are turned off by identity politics — they don’t get the ‘Jewish’ part of the Jewish state.

She bristles when JVP is called “anti-Israel,” especially because her father is Israeli, and many of her family members still live there. (“They don’t know what I do,” she said, “I don’t talk about it.”)

The right-wing Jewish groups that blame the Palestinians, President Barack Obama, The New York Times and Islam for all of Israel’s ills? JVP is their mirror image, putting all the blame on Israel. Yes, this sounds like nonsense, considering that the people in charge of Gaza aren’t exactly Quakers, but that’s the rhetoric, and it seems to be working.

More openness, greater appeal to universal values, more engagement with the kind of diverse, uncomfortable opinions and images students see on their Facebook pages, even more dialogue with groups such as JVP that make the mainstream cringe — perhaps that’s where Israel’s supporters should start, said Brous.

And with numbers like 25 percent, they have a long way to go.

Rob Eshman is publisher and editor-in-chief of TRIBE Media Corp./Jewish Journal. Email him at [email protected]. You can follow him on Twitter @foodaism.