Sen. Bernie Sanders has a long history of being tough on Israel, even to a point not matched by other left-leaning Democrats in the 2020 presidential primary field.

In recent days, Sanders has offered support for Democratic Rep. Ilhan Omar of Minnesota after she was accused of making anti-Israel, and what some said were anti-Semitic, comments. She accused the pro-Israel AIPAC of buying lawmakers and some members of Congress of having dual loyalties to Israel and the United States.

“We must not ... equate anti-Semitism with legitimate criticism of the right-wing, Netanyahu government in Israel. Rather, we must develop an even-handed Middle East policy which brings Israelis and Palestinians together for a lasting peace,” he said in a statement to the Washington Examiner.

Belen Sisa, a press officer for his presidential campaign, apologized last week for questioning whether the “American government and American-Jewish community has a dual allegiance to the state of Israel” in comments on a Facebook post saying she stood with Omar.

Among Democratic presidential primary candidates, Sens. Elizabeth Warren of Massachusetts and Kamala Harris of California have also defended Omar. “Branding criticism of Israel as automatically anti-Semitic has a chilling effect on our public discourse,” Warren said in a statement. “What I fear is going on in the House now is an effort to target Congresswoman Omar as a way of stifling that debate,” Harris said in a statement.

But other 2020 contenders were less indulgent of Omar. Sen. Kirsten Gillibrand of New York said in a statement that Omar could criticize Israel but “without employing anti-Semitic tropes about money or influence.” New Jersey Sen. Cory Booker said he found Omar’s statements “disturbing” but stressed that all forms of bigotry should be condemned, including anti-Islamic criticisms of Omar. Sen. Amy Klobuchar of Minnesota said Omar apologizing was “the right thing to do.”

Sanders, a Jewish, self-described socialist, said in a 2016 Democratic presidential primary debate that he is “100 percent pro-Israel.” But his comments about Omar and many earlier statements and actions suggest otherwise.

Sanders and some other Democratic senators wrote three letters in 2017 and 2018 that were critical of Israeli policies regarding the prosecution of a Palestinian activist, the demolition of a Palestinian village, and U.S. involvement in the “ongoing humanitarian crisis in the Gaza Strip."

But Booker, Harris, Gillibrand, and Klobuchar did not join the letters. Warren joined two of them.

Last May, Sanders condemned the killing of more than a dozen Palestinians by Israeli forces during conflict in Gaza. In June, he published a video of Palestinians in Gaza describing their difficult lives in the territory.

Sanders has asserted that “the founding of Israel involved the displacement of hundreds of thousands of people already living there, the Palestinian people.”

Despite voting in support of a June 2017 resolution that called to move the U.S. Embassy in Israel to Jerusalem, Sanders in December 2017 criticized Trump’s plan to recognize Jerusalem as the capital of Israel, arguing that “it would dramatically undermine the prospects for an Israeli-Palestinian peace agreement.”

He told the Intercept in 2017 that he would consider voting to cut U.S. aid to Israel. “The U.S. funding plays a very important role, and I would love to see people in the Middle East sit down with the United States government and figure out how U.S. aid can bring people together, not just result in an arms war in that area,” he said.

Republican strategist Alex Conant of consulting firm Firehouse Strategies told the Washington Examiner that Sanders’ positions on Israel, his aide’s comments, and his reaction to the Omar controversy could be trouble for him in the 2020 Democratic presidential race.

“Democrats desperately want to defeat Donald Trump and will be weary of a candidate who has such glaring vulnerabilities,” Conant said.

Christopher Budzisz, director of the Loras College Poll and an associate professor at the Iowa college, told the Examiner that Sanders’ Israel stances are more relevant in the general election and likely won’t affect Iowa caucus-goers’ voting decisions.

If the controversy over Omar persists, however, “the difficulty for Sanders is if it becomes less about Israel and more about anti-Semitism,” Budzisz said.

Polling suggests that Sanders has some leeway to criticize the Israeli government without losing significant support from Jewish voters.

Jim Gerstein, a Democratic pollster and founding partner of GBA Strategies, told the Examiner that Jewish Americans vote overwhelmingly Democratic and generally don’t base primary decisions on Israel stances.

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A candidate must pass a “threshold” of being sufficiently supportive of Israel in order to earn support from Jewish voters, but issues such as healthcare and the economy are more important to their voting decisions, GBA’s 2018 post-election survey of Jewish voters for liberal advocacy group J Street found.

“It is an easy threshold for a candidate to pass to be seen as sufficiently supportive of Israel,” Gerstein said, asserting that every Democratic presidential candidate has met that requirement.

A Mellman Group poll from October 2018 found that while 92 percent of Jewish voters consider themselves pro-Israel, 59 percent said that they are critical of some or many of the Israeli government’s policies.

Speaking at a 2017 conference for J Street, he said that it is important for progressives to “acknowledge the enormous achievement of establishing a democratic homeland for the Jewish people after centuries of displacement and persecution.”

Sanders’ campaign declined to comment on his Israel stances and campaign strategy, pointing instead to previous Sanders statements.