WASHINGTON — Even as critics intensify their efforts to depict him as unfit to protect the U.S.-Israel relationship, Chuck Hagel has convinced several of the most prominent Jewish Democratic lawmakers to endorse his nomination to lead the Pentagon.

Since rumors of his nomination first surfaced in December, opponents have argued to varying degrees that Hagel is anti-Israel and even anti-Semitic. At the center of many of the attacks has been his 2006 comment to an interviewer that the “Jewish lobby” intimidates many people in Washington.

In recent days, Hagel has secured endorsements from three of the most identifiably Jewish and pro-Israel Democratic lawmakers: U.S. Sens. Charles Schumer (D-N.Y.) and Barbara Boxer (D-Calif.), as well as U.S. Rep. Debbie Wasserman Schultz (D-Fla.), the chairwoman of the Democratic National Committee.

The endorsements follow several discussions with lawmakers during which Hagel is said to have expressed regret for the “Jewish lobby” comment. In those discussions, he also assured lawmakers that he is committed to preventing Iran from obtaining a nuclear weapon.

“In our conversation, Sen. Hagel made a crystal-clear promise that he would do ‘whatever it takes’ to stop Tehran from obtaining nuclear weapons, including the use of military force,” Schumer said in a statement regarding his Monday meeting with Hagel. “He said his ‘top priority’ as Secretary of Defense would be the planning of military contingencies related to Iran.”

Obama’s formal nomination of Hagel on Jan. 7 only intensified the battle lines over the former Nebraska senator and Vietnam War hero.

That day, one of his most prominent critics, Elliott Abrams, told NPR that Hagel “appears to be” an anti-Semite. Less than a week later, on the Jan. 13 broadcast of “Meet the Press,” one of Hagel’s more prominent defenders, Colin Powell, called such attacks “disgraceful.”

Powell’s rejoinder was all the more extraordinary because he and Abrams were the top shapers of foreign policy in the George W. Bush administration — Powell as secretary of state in the first term and Abrams as the deputy national security adviser who took the lead on Middle East issues.

“When they go over the edge and say because Chuck said Jewish lobby he is anti-Semitic, that’s disgraceful,” Powell said. “We shouldn’t have that kind of language in our dialogue.”

There was little sign that the sharp exchanges would fade ahead of confirmation hearings likely to take place as early as next month. The Emergency Committee for Israel, a group that has consistently opposed Obama’s Israel policies and backed only GOP candidates, ran a full-page ad in The New York Times on Tuesday urging readers to call Schumer and the junior senator from New York, Kirsten Gillibrand, also a Democrat, and tell them not to confirm Hagel.

“Ask them to put country ahead of party,” the ad said.

The Zionist Organization of America and Christians United for Israel continue to advocate against Hagel on Capitol Hill and through social media. On Tuesday they were joined by one of the preeminent political action committees, NORPAC, which asked its activists to tell their senators that they oppose Hagel’s nomination.

Liberal Jewish groups such as Americans for Peace Now, J Street and the Israel Policy Forum have backed Hagel. Centrist groups like the Anti-Defamation League and the American Jewish Committee at one time seemed poised to fight the choice — but not now.

For example, in letters to Democratic senators before the formal nomination, AJC pressed them to urge Obama not to nominate Hagel. Since the nomination, however, the group has said it is ‘concerned’ but does not formally oppose the nomination.”

The American Israel Public Affairs Committee has not made any public statement on the matter, and Hill insiders say its officials also have been silent on Hagel in their private encounters. Josh Block, the former AIPAC spokesman who now runs The Israel Project, has been directing reporters to material critical of Hagel, but from his private email account.

Hagel, meanwhile, has barely granted any interviews — a JTA request is pending — but has reached out to top Jewish lawmakers to explain what appear to be past equivocations on Iran policy and to apologize for remarks in which he referred to an “intimidating” Jewish lobby.

Calling the term “Jewish lobby” a “very poor choice of words,” Hagel said in a letter to Boxer that “I used that terminology only once, in an interview. I recognize that this kind of language can be construed as anti-Israel.”

He delivered a similar apology over the phone last week to Wasserman Schultz, a flag bearer for Jewish causes among Democrats — it was her freshman legislation that in 2006 established Jewish Heritage Month.

“He realized some of the things he had said previously were offensive and inappropriate,” Wasserman Schultz told JTA.

Hagel already had the backing of two leading Jewish senators, Carl Levin (D-Mich.) and Dianne Feinstein (D-Calif,), but insiders considered Schumer’s endorsement critical. Schumer has noted repeatedly to Jewish audiences that his name derives from the Hebrew word “shomer,” or guardian, and that he sees Israel’s security as his calling.

Boxer also is a go-to Jewish lawmaker — she was the lead on a bill last year that enhanced the U.S.-Israel security relationship.

“After speaking extensively with Sen. Hagel by phone last week and after receiving a detailed written response to my questions late today, I will support Sen. Hagel’s nomination as Secretary of Defense,” Boxer said in a release late Monday. “First and foremost, he has pledged without reservation to support President Obama’s polices — policies that I believe have made our world safer and our alliances stronger.”

Beyond his remarks regarding a “Jewish lobby,” the issues that had exercised Boxer and Wasserman Schultz — as well as some pro-Israel groups — had to do with Hagel’s past skepticism of the efficacy of unilateral sanctions as a means of keeping Iran from developing a nuclear weapon, as well as his wariness of a military option in the same case.

In his letter to Boxer, Hagel reiterated his preference for multilateral sanctions, noting his past support, but added that unilateral sanctions in some instances were “necessary.” He did not mention the possibility of a strike.

But Wasserman Schultz said that in her phone call with Hagel, “he said that all options should be on the table, including a military option.”

In both interactions, Hagel also noted his solid Senate record voting to fund defense assistance to Israel.

Wasserman Schultz pressed Hagel to explain why he had not signed a number of letters organized by the pro-Israel and Jewish communities, particularly an American Jewish Committee-backed letter in 1999 asking Russian Jewish President Boris Yeltsin to address the rise of violent anti-Semitism. The letter drew 99 signatories out of 100 senators; Hagel was the only one to pass.

The Florida lawmaker told JTA that she was satisfied with his response — that as a senator he preferred not to write foreign leaders, but over the years wrote Presidents Bill Clinton and George W. Bush to express his concern about anti-Semitism overseas.

Nonetheless, his insistence on standing apart apparently gave Wasserman Schultz pause.

“I told him, when it’s 99 to 1, everybody can’t be wrong,” she said.

Left untreated in Hagel’s interactions with Wasserman Schultz and Boxer was the hostile worldview that critics have said holistically underpin Hagel’s history with Israel and its supporters.

“This is not a mere choice of words,” wrote Jennifer Rubin, the Washington Post’s conservative blogger, referring to Hagel’s apology to Boxer for using “Jewish lobby.”

“Hagel said that the Jewish lobby ‘intimidates’ lawmakers,” wrote Rubin, a mainstay of the effort to keep Hagel from the top defense post. “Which lawmakers? Was he intimidated?”

Hagel made the “Jewish lobby” comment in an interview with Aaron David Miller, the author and former U.S. peace negotiator. Hagel also told Miller in the same interview that he was an “American senator,” not an Israeli one.

In her JTA interview, Wasserman Schultz paused before answering whether she agreed with Hagel that the pro-Israel lobby intimidates. She repeated the question and then said, “In our conversation he expressed regret and was apologetic that the reference was hurtful.”

Boxer in a conference call said those who read imputations of disloyalty against pro-Israel groups into Hagel’s remarks “were reading too much.”

“I don’t think he thinks people are less loyal,” she said, adding, “I don’t agree with what he said; I was concerned with what he said.”

Boxer noted that Hagel’s letter to her had arisen out of a conversation she had with Hagel. She thought it was important to get his thoughts in writing, and he agreed.

“He told me, if there’s one thing in his life that he could take back, it’s that,” the California senator said.

Writing to Boxer, Hagel did not precisely retreat from his impassioned comments in 2006, when he said during Israel’s war with Hezbollah that “extended military action is tearing Lebanon apart, killing innocent civilians, devastating its economy and infrastructure.”

Instead, he said that in that war, “Israel was defending itself” but added, “these attacks were not perpetrated by the Lebanese government, which remains an important partner to the United States.”