After the 1967 War, when Israel conquered the remaining 22 percent of Palestine, as well as the Sinai Peninsula from Egypt and the Golan Heights from Syria, Israel illegally established settlements in the territories it occupied and created a regime with separate laws for different groups — Israelis and Palestinians — living in the same territory. In 1980, Israel formally annexed East Jerusalem. As with Israel’s settlement activity, there was some international finger wagging and condemnation, but American financial and military backing for Israel only strengthened.

In 1993, the Oslo Accords granted limited autonomy to Palestinians in a scattering of disconnected islets. The accords did not demand the dismantling of Israeli settlements or even a halt to settlement growth. The first American plan for Palestinian statehood was presented by President Bill Clinton in 2000. It stated that large Israeli settlements would be annexed to Israel and that all Jewish settlements in occupied East Jerusalem would also be annexed. The Palestinian state would be demilitarized and contain Israeli military installations as well as international forces in the Jordan Valley that could be withdrawn only with Israel’s consent. As with the “deal of the century,” this plan, which formed the basis of all subsequent ones, gave the Palestinians increased autonomy and called it a state.

There are now more Palestinians than Jews living in the territory under Israel’s control, according to the Israeli military. Whether in Mr. Trump’s vision or Mr. Clinton’s, American plans have confined most of the majority ethnic group into less than a quarter of the territory, with restrictions on Palestinian sovereignty so far-reaching that the outcome should more appropriately be called a one-and-a-half-state solution.

Mr. Trump’s plan has many severe faults: It prioritizes Jewish interests over Palestinian ones. It rewards and even incentivizes settlements and further dispossession of the Palestinians. But none of these qualities represent a fundamental break from the past. The Trump plan merely puts the finishing touches on a house that American lawmakers, Republican and Democrat alike, spent dozens of years helping to build. During the last several decades, as Israel slowly took over the West Bank, putting more than 600,000 settlers in occupied territory, the United States provided Israel with diplomatic backing, vetoes in the United Nations Security Council, pressure on international courts and investigative bodies not to pursue Israel, and billions of dollars in annual aid.

Some of the Democrats now running for president have spoken of their disapproval of Israeli annexation, even as they propose nothing to stop it. Thus a mainstream Democrat like Senator Amy Klobuchar could declare her opposition to annexation and sign a letter criticizing the Trump plan for its “disregard [of] international law,” when she had also co-sponsored a Senate resolution “expressing grave objection” to a 2016 United Nations Security Council resolution that demanded Israel halt illegal settlement activity. Other Democrats, such as Senator Elizabeth Warren and Pete Buttigieg, say they would be unwilling to provide American financial support for Israeli annexation. But that is little more than a slick formulation that allows them to sound tough while threatening nothing, since American assistance to Israel would not, in any event, go directly toward the bureaucratic tasks involved, such as transferring the West Bank land registry from the military to the Israeli government.