The trouble for Mr. Netanyahu is that the polling figures look no better this time around. Should Mr. Gantz emerge as prime minister, Mr. Netanyahu would not be able to use Parliament to try to block a threatened indictment. Attorney General Avichai Mandelblit — a Netanyahu appointee — has scheduled a hearing on whether to charge him with three counts of fraud and breach of trust and one of bribery for Oct. 2 and 3.

Mr. Netanyahu has also failed so far in this round to get Mr. Trump’s blessing. The White House response to his pledge to annex the Jordan Valley, nearly a third of the West Bank, was that there is “no change in United States policy at this time,” possibly because Mr. Trump and his son-in-law, Jared Kushner, plan to reveal their long-promised Middle East peace plan soon after the Israeli election.

Mr. Netanyahu, moreover, has lost a strong ally in John Bolton, the national security adviser pushed out this week, and Mr. Trump’s evident willingness to meet with Iran’s president, Hassan Rouhani, puts him at odds with Mr. Netanyahu’s unrelenting hostility toward Tehran. Mr. Netanyahu’s hope to get a boost from his meeting with Mr. Putin on Thursday was also blunted when Russia reacted frostily to his plan to annex the Jordan Valley, warning that this would “sharply escalate tensions in the region.”

That it would, and for no good reason. The Israeli military establishment, Israeli public opinion and Mr. Netanyahu’s challenger in the election, Mr. Gantz, a retired three-star general, have long held that Israel must retain military control of the Jordan Valley for some period after a peace treaty is signed, effectively maintaining a buffer between the Palestinians and Arab lands to the east. The valley, currently home to about 65,000 Palestinians and 11,000 Jewish settlers, remained under Israeli military control under the Oslo peace accords signed in 1993.

But outright annexation would be a blatant violation of international norms and an affront to the Palestinians that would snuff what glimmer of possibility remains for a negotiated two-state solution to the Israeli-Palestinian conflict.