When Reps. Alexandria Ocasio-Cortez, Rashida Tlaib, and Ilhan Omar endorsed Sen. Bernie Sanders for president, all three cited the candidate's policy platform and his call for a "political revolution."

But the key endorsements were also motivated by personal loyalty and a mutually beneficial political relationship between the lawmakers.

Sanders has stepped in to defend all three lawmakers, two of whom are the first Muslim women to serve in Congress, when they've been attacked by the president and sometimes by members of their own party.

"At every turn, it has been Bernie Sanders who immediately leapt to [Omar's] defense publicly and was often, I think, the first to do so," Faiz Shakir, Sanders' campaign manager, told Insider.

The congresswomen appear to have developed a personal relationship with Sanders. Ocasio-Cortez refers to him as "tio Bernie" and Tlaib calls him "amo Bernie," which is Arabic for uncle.

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When Reps. Alexandria Ocasio-Cortez, Rashida Tlaib, and Ilhan Omar endorsed Sen. Bernie Sanders for president, all three cited the candidate's policy platform and his call for a "political revolution." But the key endorsements were also motivated by personal loyalty and a mutually beneficial political relationship between the lawmakers.

Sanders has had all of their backs at controversial moments when few defended them. In return, three-fourths of the so-called "Squad" will have his in 2020. (The fourth squad member — Rep. Ayanna Pressley of Massachusetts — hasn't yet endorsed anyone in the 2020 race.)

In September 2018, Omar told The Intercept that she was in Sen. Elizabeth Warren's "wing" of the Democratic Party. And she brushed aside Sanders' potential 2020 bid.

"I actually believe that ship might have sailed," Omar said on the outlet's podcast.

But since then, Omar has relied on Sanders in a few crucial moments. He was one of the few senators to defend Omar amid backlash against a series of comments she made earlier this year about Israel that many perceived as anti-Semitic.

"It is not anti-Semitic to be critical of a right-wing government in Israel," said Sanders, who is Jewish, adding that Omar may "need to do a better job speaking to the Jewish community," but that he wanted "a Muslim member of Congress not to be attacked every single day in outrageous, racist remarks."

Sanders added that while he had "respect" for Omar, he had only talked to her "about twice in my life."

Faiz Shakir, Sanders' campaign manager, cited the senator's support of Omar as motivation for her endorsement.

"Probably there's no single politician in America who's been more vilified by Donald Trump than [Omar], constantly and repeatedly," Shakir told Insider in a recent interview. "At every turn, it has been Bernie Sanders who immediately leapt to her defense publicly and was often, I think, the first to do so."

He added that the lawmakers "appreciate" that Sanders has been a key ally for them in Washington.

"And I think they understand and appreciate that he's been fighting for them and they see eye-to-eye on building this multi-racial working class coalition," Shakir said.

Sanders similarly defended Tlaib when the president and other Republicans falsely claimed that Tlaib celebrated the Holocaust. (Tlaib instead said the knowledge that her Palestinian ancestors' displacement resulted in "a safe haven for Jews" after World War II gave her a "calming feeling.")

"Stop your ugly attacks against Muslim women in Congress. You are taking Rep. @RashidaTlaib's comments out of context and should apologize," the senator said in a tweet directed at Trump.

From L to R: Reps. Rashida Tlaib, Ilhan Omar, Ayanna Pressley, and Alexandria Ocasio-Cortez AP Photo/J. Scott Applewhite

When Ocasio-Cortez exchanged barbs with House Speaker Nancy Pelosi earlier this year, Sanders also stepped in, however carefully. The senator said Pelosi was being "a little bit" too tough on the Squad when she minimized the lawmakers' power on the Hill.

"You cannot ignore the young people of this country who are passionate about economic and racial and social and environmental justice," Sanders told NBC News. "You got to bring them in, not alienate them."

'Uncle Bernie'

The congresswomen appear to have developed a personal relationship with Sanders. The Bronx lawmaker refers to him as "tio Bernie" and Tlaib, whose family is Palestinian-American, calls him "amo Bernie," Arabic for uncle.

In her Sunday video announcing her endorsement, Tlaib credited Sanders with defending the Squad from President Donald Trump's repeated attacks.

"I think Amo Bernie, when he saw, not just myself but my other sisters in service being attacked by this president, this bully, for him there was no hesitation," Tlaib said. "He jumped on board and said, 'What can I do to uplift you all? What can I do to support you all?"

A source close to Ocasio-Cortez told Insider that the two built "amazing chemistry" beginning on the campaign trail last year in Kansas and Michigan where they took "four-, five-, six-hour car rides" between events.

Tlaib and Omar, the first two Muslim women to serve in Congress, have now endorsed one of the two Jewish candidates in the 2020 race (the other being Marianne Williamson).

Sanders has implied that his religious identity can be "helpful" in fending off the kind of criticism both Omar and Tlaib have faced from across the political spectrum.

"Being Jewish may be helpful in that regard," Sanders told the audience at a J Street conference on Monday. "It will be hard for anybody to call me, whose father's family was wiped out by Hitler, an anti-Semite."