Ilhan Omar, a candidate for State Representative for District 60B in Minnesota, gives an acceptance speech on election night, November 8, 2016 in Minneapolis, Minnesota. 
Omar, a refugee from Somalia, is the first Somali-American Muslim woman to hold public office. / AFP / STEPHEN MATUREN        (Photo credit should read STEPHEN MATUREN/AFP/Getty Images)
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Ilhan Omar, a candidate for State Representative for District 60B in Minnesota, gives an acceptance speech on election night, November 8, 2016 in Minneapolis, Minnesota. Omar, a refugee from Somalia, is the first Somali-American Muslim woman to hold public office. / AFP / STEPHEN MATUREN (Photo credit should read STEPHEN MATUREN/AFP/Getty Images)
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(CNN) —  

Democrats are entering the 2020 election cycle with many of their leading presidential contenders increasingly willing to break with a pro-Israel foreign policy orthodoxy that guided the party for a generation.

The new crop of progressive political stars in the House and a base more sympathetic to the Palestinians than ever before helped push a half-dozen White House aspirants to break with the pro-Israel lobby last week on a major bill, even as it passed with support from Minority Leader Chuck Schumer and other high-ranking Democratic officials.

But the simmering divisions and debates inside the party blew up on social media Sunday night, when Minnesota Rep. Ilhan Omar suggested in a series of flippant tweets that the top House Republican’s support for Israel was “all about the Benjamins” – or tied to financial backing offered by the right-leaning American Israel Public Affairs Committee.

Omar’s comments were denounced by members of both parties as “anti-Semitic” and, by Monday afternoon, she had responded to Democratic leadership’s condemnation with an apology, saying in a statement posted online, “I unequivocally apologize.” Earlier in the day, a pair of Democratic House newcomers sought to gather signatures for a letter rebuking Omar over her tweets and, in a move likely to escalate the controversy, her support for the Boycott, Divest and Sanctions movement – known as BDS – against Israel in response to its treatment of Palestinians.

“Such positions,” Democratic Reps. Josh Gottheimer and Elaine Luria wrote, “are, at their core, anti-Semitic.”

The blow-up threatens to further complicate an already knotty question facing progressives who have spent years now carefully questioning what they view as a political establishment that is too deferential and unwilling, over domestic political concerns, to criticize the Israeli government.

Contrary to Omar’s claim, AIPAC does not donate to candidates. It does, however, spend millions lobbying elected officials – a distinction she failed to make – and does, as described on its own website, ask its would-be “Congressional Club” members to “commit to giving political contributions in a clearly pro-Israel context to candidates running for the United States House of Representatives and/or United States Senate.”

“It’s undeniable that money plays a huge role in our politics. Also true that tropes about Jewish money have been used for centuries to target Jews,” Sen. Bernie Sanders’ foreign policy adviser Matt Duss tweeted on Monday morning. “Progressives need to be extremely aware of that history and avoid those tropes as we talk together about how to fix our politics.”

Sanders, who is Jewish, has been among the likely 2020 contenders most willing to denounce the Israeli government over its treatment of the Palestinians.

The ongoing political shift came clearly into focus last week when nearly all of the Democratic presidential hopefuls – with Sen. Amy Klobuchar a notable exception – voted against a Senate bill that would allow state and local governments to withhold contracts from those who participate in BDS. Most of them took the same position in explaining their opposition to the bill: They oppose efforts to boycott Israel, they said, but they feared the measure violated First Amendment rights.

“There are ways to combat BDS without compromising free speech, and this bill as it currently stands plainly misses the mark,” New Jersey Sen. Cory Booker – who had co-sponsored a similar bill as recently as November — said in a statement last week to Jewish Insider.

Most of the other Democratic presidential candidates and potential candidates in the Senate – including Sanders, California Sen. Kamala Harris, New York Sen. Kirsten Gillibrand and Ohio Sen. Sherrod Brown – opposed the legislation, all citing free speech concerns that overshadowed their opposition to the boycott efforts.

“I believe in free speech. And I do not support BDS but I think the steps to outlaw go too far,” Massachusetts Sen. Elizabeth Warren told CNN recently.

The votes put the party’s 2020 field largely at odds with Schumer, the New York Democrat, who backed it. They also failed to sink the effort which easily passed with support from both parties. It is unclear if House Democrats will bring up the bill for consideration.

But in voting in near lockstep against it, the presidential contenders highlighted a shift that has been gaining steam among Democrats for years.

In 2018, the Pew Research Center found that 27% of Democrats said their sympathies lied with Israel, while 25% said the Palestinians – with the rest saying neither. That was a sharp drop from the 43% who chose Israel just two years earlier. Younger and more liberal Democrats, in particular, said they were more likely to side with the Palestinians. And some companies that cater to a younger clientele have also shifted their positions in response to Israeli government actions: A