Among liberal Democrats, there is now almost an even split between those saying they sympathize with the Israeli side and the Palestinian one, according to Gallup.

And a Pew survey conducted in April found that Jewish Americans were far more likely than Christians to say that Mr. Trump was “favoring the Israelis too much.” Forty-two percent of Jewish respondents to the national poll said so, compared with just 6 percent saying he was too supportive of Palestinians. Only about one in four Christians said Mr. Trump was overly supportive of Israel.

Jewish voters are among the Democratic Party’s most loyal supporters. In the 2018 midterm elections, four out of every five Jewish voters said in exit polls that they had supported a Democratic candidate for Congress.

And while Jewish Americans account for just 2 percent of the overall vote, they represent an outsize share of the Democrats’ donor base. According to an analysis by The Forward, a Jewish publication, roughly 5.5 percent of all donors to Democratic presidential candidates in the first half of this year were Jewish, and they accounted for 7 percent of all funds given. (The Forward used several methods, including a research tool called the Distinctive Jewish Names list, to identify donors who were most likely Jewish in campaign finance reports.)

The Forward found that the Democratic presidential candidate receiving the most donations from Jewish backers this cycle has been Mr. Buttigieg, even as he has issued sharp critiques of Mr. Netanyahu.

“You can be committed to the U.S.-Israel alliance without being supportive of any individual choice by a right-wing government over there,” Mr. Buttigieg said at the J Street conference on Monday.

Mr. Sanders, who would become the country’s first Jewish president if elected, railed against giving “carte blanche to the Israeli government, or for that matter to any government at all.”