Donald Trump is the presumptive GOP U.S. presidential nominee because he saw a market that wasn’t being served. The market was for a Republican who opposed free trade, opposed immigration, opposed the Iraq War and denounced America’s political system as corrupt. The market wasn’t new. For years, polls had showed that ordinary Republicans liked economic globalization, military occupations and big money donations less than GOP elites. But because GOP elites wielded so much influence in selecting nominees, the supply of Republican presidential candidates had not met the market’s demand.

Then along came Trump, who leveraged his celebrity to dominate cable television, thus winning vast quantities of “free media.” Having overcome the financial limitations that had felled prior outsider candidates, he pushed a message that appalled GOP elites, and most Democrats. But ordinary Republicans — or least at a plurality of them — loved it. They had finally found a top-tier presidential candidate who said what they wanted to hear.

What does this have to with Israel? More than you might think, because just as Trump saw an unserved market among rank-and-file Republicans on trade, immigration and military intervention, there’s an unserved market among grassroots Democrats for a candidate who is critical of Israel.

The polling illustrates it. According to a new Pew Research Center poll, 54 percent of Americans say they sympathize with Israel as opposed to only 35 percent who sympathize either with the Palestinians, with neither side or with both sides. But among liberal Democrats, the figures are reversed: 33 percent sympathize with Israel while 57 percent sympathize with the Palestinians, neither side or both. Moderate and conservative Democrats harbor views more in line with the country as a whole.

But the percentage of Democrats who identify as “liberal” has risen by 15 points since 2000. And younger Democratic voters are significantly more likely to call themselves “liberal” than older ones, which suggests that the Democratic electorate will shift leftward in the years to come.

The more it does, the bigger the market opportunity for a Democratic politician who is critical of Israeli policy. Today, most Democratic politicians support the two state solution. But they justify it overwhelmingly in the language of Israeli self-interest. It’s rare to hear Democratic politicians talk much about Palestinian human rights or express much criticism of Israeli behavior. It’s even rarer to hear Democratic politicians support any pressure on the Jewish state.

Hillary Clinton is a good example. Last October, she denounced a “wave of attacks against Israelis” without even acknowledging that any Palestinians had died. In a letter this month, she boasted about having “made sure the United States blocked Palestinian attempts at the UN to unilaterally declare statehood.” (What, exactly, is “unilateral” about more than one hundred countries voting for Palestinian statehood, she didn’t say.)

Had Bernie Sanders challenged Hillary on Israel earlier in the campaign, he might have exposed the gap between her views and those of most liberal voters. But he mostly stuck to safe, brief, vague platitudes. Not until mid-April, on the eve of the New York primary, did Sanders challenge Clinton on Israel in a Democratic debate. When he talked about the “houses decimated, health care decimated, schools decimated” in the Gaza Strip and declared that, “there comes a time when if we pursue justice and peace, we are going to have to say that Netanyahu is not right all of the time,” the media responded with shock. “Bernie Sanders smashes the Israel status quo,” declared CNN. Vox added that, “Bernie Sanders just shattered an American taboo on Israel. But then, when the campaign left New York, Sanders largely dropped the subject.

Sooner or later, however, a Democratic presidential contender will make criticism of Israeli policy a consistent feature of his campaign. He’ll do it to stand out from his opponents, who hew to a conventional, AIPAC-like, position. And he’ll do it to curry favor with the liberal millennials who increasingly define the Democratic party base. Given the growing links between Black Lives Matter activists and their Palestinian counterparts, a more critical perspective on Israel policy could help among younger African Americans too.

The analogy with Trump is not exact. Israel is unlikely to ever matter as much to Democratic voters as immigration and trade do to Republican ones. But Trump has shown that when a party’s elite does not represent its voters, renegade candidates will eventually exploit the gap. In the Democratic Party on Israel, it’s only a matter of time.