The U.S.Israeli alliance is getting testy.

The U.S.-Israeli relationship is getting testy. In recent weeks, the Biden administration and the right-wing government of Israeli Prime Minister Benjamin Netanyahu have reportedly clashed on a number of issues, from Netanyahu’s plans to overhaul the nation’s judicial system to his efforts to expand settlements in the West Bank.

But the strained relationship is about more than just policy disagreements; it is an unavoidable ideological rift between U.S. Democrats and the increasingly conservative Israeli nation that will fundamentally alter the decades-long alliance.

Israel started out dominated by secular, Ashkenazi Jews who emigrated from Western Europe. They were largely left-leaning, so for decades after gaining its independence in 1948, the country was ruled by the social democratic Labor Party in coalition with other, smaller leftist parties.

That changed as more Mizrahi Jews emigrated to the country from North Africa and the Middle East, leading to the center-right Likud’s shocking victory in 1977. These voters tended to be more religious, hawkish and nationalistic than the center-left Ashkenazi.

Demographic changes since then have pushed Israeli politics even further to the right. Massive emigration from the former Soviet Union brought secular, right-leaning Jews who tended to back the Likud or Russian-immigrant Israel Beiteinu parties. Emigration from elsewhere tended to draw religious Jews who wanted to settle in the West Bank, which they refer to by its biblical names of Judea and Samaria. These voters often back parties well to the right of Likud.

High birth rates among ultra-Orthodox Jews are sealing the religious right’s political power. Secular Jewish women now have an average of about two children, only slightly higher than fertility rates in the United States. But religious Jewish women have four children on average, and ultra-Orthodox Haredi women have more than six. This explains why the Haredi population makes up only 13 percent of Israel today, while Haredi children compose 24 percent of the population younger than 4.

This means the influence of the religious right will inevitably grow in coming elections. Israeli academic Dan Ben-David documents this inevitable rise, noting that Haredi voters turn out at higher rates and vote almost unanimously for Haredi parties. Those parties, United Torah Judaism and Shas, received 14 percent of the vote in last year’s elections. That total will likely break 20 percent when Haredi toddlers turn 18 in the 2040s.

The pro-settlement, non-Haredi right is also growing. Its primary party, the Religious Zionist Party, won almost 11 percent of the vote, but this underestimates the role settler sentiment plays on the right. Jewish West Bank settlements gave 81.6 percent of the vote to parties backing Netanyahu. Netanyahu’s Likud still wins a significant share of that vote but would clearly lose ground if it backed President Biden’s position on restricting settlement growth. Netanyahu cannot abandon his base.

These facts mean that the Israeli politics Democrats prefer – center-left governments dominated by residents of the liberal Tel Aviv region – is no longer possible. Such a government is already essentially impossible, because it would require support from everyone from left-wing, pro-Palestinian Arab parties in the Joint List to right-leaning parties such as Israel Beiteinu. Moreover, that coalition’s share of the vote will inevitably decline as the Haredi and settler populations grow.

These groups do not want left-wingers halting their political aspirations. That is why judicial reform is such an integral part of the Netanyahu government’s platform. The Israeli Supreme Court rarely strikes down a law, but when it does it almost always does so from the perspective of the center-left. The reform bill would change that by giving the government more power to select who serves on the court and curbing its authority to overturn laws passed by the Knesset (Israel’s parliament). Biden has criticized the bill, but Netanyahu cannot abandon it without breaking his coalition apart.

These pressures will only intensify. Right-wing voters want what would appear to many Americans as special privileges for religious populations, such as exemptions from the otherwise universal (for Jewish Israelis) military draft and extensive subsidies for the Haredi community. They unapologetically declare they want Israeli sovereignty over the entire West Bank. And they want a hawkish policy toward Iran that brooks no compromise.

Netanyahu will eventually leave politics. But these political pressures and voices will not.

Republican administrations will likely see no problem with this. They will see the emerging right-wing, religious bloc in Israel as a mirror image of their own, right down to the implacable hostility it faces from Israel’s elite institutions.

But Democratic administrations will surely remain aghast at what’s happening in the country. They will have to choose between their center-left principles and continuing the historically strong alliance between the United States and Israel. Given that liberal Democrats already sympathize more with Palestinians than Israelis, maintaining the alliance will be increasingly difficult for any Democratic president.

Before long, the long-standing bipartisan support for Israel in the United States could be a thing of the past.