Several of Mr. Biden’s top advisers, including Secretary of State Antony J. Blinken and the national security adviser, Jake Sullivan, worked for Mr. Obama and have vivid memories of Israel’s lobbying campaign against the Iran deal.
Mr. Dermer brushed aside the battles of the past as “totally irrelevant” to his relationships with the administration today. “I don’t see it as a cloud hanging over anything,” he said in a telephone interview on Monday.
Iran, he noted, has receded as a bone of contention between the United States and Israel. Mr. Biden’s attempts to revive the nuclear talks have faded, and Hamas, which led the deadly Oct. 7 assault on Israeli civilians and soldiers, is backed by the Iranians. The president sent aircraft carriers to the eastern Mediterranean to deter Iran and its Lebanese proxy group, Hezbollah, from entering the war against Israel.
“I don’t think the coordination and cooperation has ever been better, certainly not in a time of war,” Mr. Dermer said. “They understand where we are; we understand where they are.”
That was not the case during the Obama years. In 2014, during a previous Israeli military operation in Gaza, the State Department said it was “appalled” by what it called a “disgraceful” strike on a U.N. school. Israeli officials seethed at the language, which they felt was wholly unjustified.
White House aides also fumed that Mr. Dermer tilted consistently toward the Republicans, who are more favorable to Mr. Netanyahu and his positions. Mr. Dermer had much warmer relations with President Donald J. Trump, who withdrew from the Iran nuclear deal, did not object to the Israeli settlements, proposed Israeli annexation of large parts of the West Bank and moved the U.S. embassy to Jerusalem, as Israel had long requested.
Mr. Dermer, analysts said, has a sophisticated grasp of how the war is complicating domestic politics for Mr. Biden, with progressive Democrats and Muslim and Arab American voters balking at his embrace of Israel. Given Mr. Dermer’s close ties to Mr. Trump, who is running again for president, some question whether he would counsel Mr. Netanyahu to take Mr. Biden’s sensitivities into account.
“The administration has to look at Dermer as a double-edged sword,” Mr. Miller said. “On the one hand, they have a very high-level conduit to the prime minister. On the other hand, he has a demonstrated capacity of behaving in a way that doesn’t acknowledge reciprocity between the United States and Israel.”
At one level, Mr. Dermer’s membership in the war cabinet is surprising. Born and raised in Miami Beach, he moved to Israel after graduate school and did not serve in the Israeli military. Three of the cabinet members are retired generals, while Mr. Netanyahu served in a special forces unit as a young soldier.
But on another level, it is predictable, given Mr. Dermer’s longstanding ties to Mr. Netanyahu, who is widely known as Bibi. He has advised the prime minister since 2000, whether from Washington or Jerusalem, and is viewed as his alter ago — or, as the Jewish online magazine Tablet once memorably put it, “Bibi’s Brain.”
“He made sure Dermer was a part of” the war cabinet, said Anshel Pfeffer, who wrote a biography, “Bibi: The Turbulent Life and Times of Benjamin Netanyahu.” He added, “It’s telling that the only person he trusts on it is Ron Dermer, who has little or no military experience.”
As ambassador from 2013 to 2021, Mr. Dermer was an influential player in Washington, not only in diplomatic circles but also in political ones. He cultivated lawmakers on Capitol Hill, especially Republicans, working with them to arrange a speech to a joint session of Congress by Mr. Netanyahu in 2015, during which he branded Mr. Obama’s proposed nuclear agreement a “very bad deal.”
Mr. Dermer later worked closely with Mr. Trump’s son-in-law, Jared Kushner, on the Abraham Accords, which normalized Israeli relations with the United Arab Emirates and Bahrain. That deal prioritized Israel’s relations with its Arab neighbors over a two-state settlement with the Palestinians.
“He’s the ultimate plenipotentiary guy,” said Michael B. Oren, who preceded Mr. Dermer as Israel’s ambassador, using the diplomatic term for an envoy invested with full authority to act on his government’s behalf abroad.