On its surface, the plan appears to build on the peace plans of yore. It revives the moribund two-state solution, and it covers all the major issues — Israel’s security, Jerusalem, the settlements, the right of return for Palestinian refugees and a $50 billion aid package for the Palestinians if they sign on, presumably financed by oil-rich Arabs recruited by Mr. Trump. And by calling it a “vision” rather than a “road map” or “peace plan,” Mr. Trump suggested, constructively, that it was open to the sort of bargaining at which he professes to be a genius.

This could well be “the last opportunity” for their own state that the Palestinians will ever have, as Mr. Trump warned, or at least the makings of the best deal they can expect. Given the plight of the Palestinian people and their historic claims to land, that may not be a just outcome, but it is perhaps becoming the realistic one. Outmaneuvered by successive Israeli governments, depleted, divided, disastrously led and at risk of being shrugged aside by some longtime Arab allies, the Palestinians are running out of options.

Yet this deal would be hard for even the most pragmatic and exhausted of Palestinians to accept. Mr. Trump may believe he’s offering a deal they ultimately can’t refuse, but, of course, they can, and it is hard to see how that outcome would benefit Israel, either, in the long term. It takes only a glance at the map of the proposed Palestinian “state,” and at some details of the plan, to see that it would not be much of a state at all. It would be a patchwork of ethnic islands, purportedly to be connected by bridges, roads and tunnels, all subject to security requirements, as defined by Israel. It would be, in other words, quite like what exists already.

Mr. Trump’s plan effectively grants Israel the right to annex nearly all Israeli settlements and the Jordan Valley. How likely that element of the plan was to be subject to good-faith negotiation with the Palestinians was suggested when Mr. Netanyahu promptly said he’d ask his cabinet to approve the annexations this weekend, although that move might be on hold. Under the terms of the plan, Israel is subject to a freeze on new settlement construction — at least, outside the existing blocs — for the next four years. Whether Israel abides by that constraint — and if it doesn’t, whether Mr. Trump attempts to enforce it — will be one test of the seriousness of this effort.

The Palestinians are allotted far less land in the Trump scheme than in any previous proposal. In exchange for the land it would annex, Israel would cede some land, including possibly transferring an area of central Israel where Arab citizens of Israel live. This is a step long favored by Israeli nationalists as a means of sharply reducing the number of Arab citizens of Israel.