The new American plan did dramatically turn the pre-election discourse away from Mr. Netanyahu’s recent indictment on charges of bribery and breach of trust, and back toward the security and diplomatic arenas, where he is far more comfortable.

But Ms. Talshir said the prime minister still needed at least a “mini annexation” — of one major settlement, say — before the election. Otherwise, she said, some right-wing voters might prefer to stay at home or vote for parties further to the right than Mr. Netanyahu’s conservative Likud party. Or the focus could go back to Mr. Netanyahu’s legal troubles.

Ambiguities and contradictions arose immediately with the presentation of the Trump plan, which is heavily weighted toward Israel. It would allow Israel to annex about 30 percent of the West Bank, including all the parts it deems important for security or as part of its biblical birthright.

In return, the plan makes the Palestinians a conditional offer of a truncated state made up of a disarmed Gaza Strip and chunks of the West Bank linked by roads and surrounded by Israeli territory. That would cast aside longstanding Palestinian hopes for an independent state that incorporated the vast majority of the West Bank and the Gaza Strip, with East Jerusalem as its capital.

Most of the world considers the settlements a violation of international law.

President Trump first introduced the plan as “a basis for direct negotiations” between Israel and the Palestinians. But he also said the United States would recognize Israeli sovereignty over the parts of the West Bank it gets to keep under the plan, saying that could be “immediately achieved.”

Adding to the confusion, Mr. Trump said Americans and Israelis would form a committee to come up with a more detailed map, suggesting a process that might take some time.