A backlash is underway within Democratic ranks after House leaders named a vocally pro-Israel Democrat to their top slot on a key panel that oversees Middle East policy, the latest reflection of bitter divisions in the party over support for the Jewish state.

Democrats on Tuesday chose Representative Jared Moskowitz of Florida to serve as the ranking member of the Foreign Affairs Committee’s Middle East and North Africa Subcommittee, elevating a lawmaker facing a tough re-election race who has called for “unwavering support” for Israel. Mr. Moskowitz has backed continued U.S. aid to Israel even as many Democrats have turned against it, and aggressively condemns critics of the Jewish state.

The selection put Mr. Moskowitz in line to lead the panel should Democrats win control of the House in November. Leaders also placed two other staunchly pro-Israel Democrats on the panel, Representatives Debbie Wasserman Schultz of Florida and Wesley Bell of Missouri, who like Mr. Moskowitz have been heavily backed by the American Israel Public Affairs Committee.

Progressives immediately condemned the moves, calling them tone-deaf and a sign that Democratic leaders have failed to grasp how voters in their own party have shifted on the issue of Israel and Gaza.

“Don’t put Israel hawks out of touch with our voters in charge of our Middle East policy,” Representative Ro Khanna, Democrat of California, warned party leaders on social media.

Some Democrats pushed back, noting that Mr. Moskowitz just last week trounced the progressive Democratic primary challenger in his South Florida district, who described himself as anti-Zionist.

But others asserted that the move was badly out of step with the party’s base.

In a series of irate posts, Benjamin J. Rhodes, a former top foreign policy adviser to President Barack Obama, wrote that Democrats were “showing zero regard for the vast majority of their own voters,” adding that their “disregard for war crimes and voter concerns could not be clearer.”

A New York Times/Siena national poll conducted in May found that 74 percent of Democratic voters opposed providing additional economic and military support to Israel, and a Pew Research Center poll in April found that eight in 10 Democrats and Democratic-leaning independents had an unfavorable view of Israel.

The furor underscored the shift underway among Democrats over support for Israel — once seen as a prerequisite for anyone who wanted a future in politics, but now regarded by many in the party as a major liability. It also reinforced the looming challenge that Representative Hakeem Jeffries, the New York Democrat and minority leader, who is in line to be speaker should his party win the House, will face trying to govern a caucus in which Israel has become a major fault line.

Last month, when Mr. Jeffries called for a “major reset” between the United States and Israel, progressives took it as a positive sign that he was finally moving in their direction on a high-priority issue that has starkly divided the party.

But the selection of Mr. Moskowitz, who initially said he would oppose a resolution to rein in President Trump’s war powers in Iran before changing his mind, appeared to have alienated them anew.

The Council on American-Islamic Relations, a Muslim advocacy organization, said in a statement that the appointment of Mr. Moskowitz was “an insult to the American people and a desperate attempt to shield Israel from accountability.”

An overwhelming majority of Democrats “want to spend American taxpayer dollars here at home, not on bombing children overseas,” the organization said, adding that Congress should “reflect the will of the American people, not the wishes of AIPAC or Benjamin Netanyahu’s racist, genocidal government.”

A spokesman for Mr. Jeffries declined to comment.

If Mr. Moskowitz were to become the chairman of the subcommittee next year, he would decide hearing topics and choose witnesses, moves that help frame the issue and set the tone for the debate about Israel. Progressives said they feared that with someone like Mr. Moskowitz leading the panel, it would not address issues such as settler violence and humanitarian aid in Gaza.

While the appointment drew outrage from progressives, top House Democrats regarded it as a politically wise move given that Mr. Moskowitz faces a challenging re-election campaign in a district that has been redrawn to lean more conservative. They also noted that it represented no real ideological change from the way the panel is currently organized.

The current ranking Democrat on the Middle East panel, Representative Brad Sherman of California, is also staunchly pro-Israel. Mr. Sherman was willing to give up his position at the request of Mr. Moskowitz, who currently leads a different subcommittee but said the move would help him with pro-Israel Jews in his re-election campaign, according to two people familiar with the arrangement. Democrats who sit on the committee agreed to the change.

Some moderate Democrats said the backlash to Mr. Moskowitz’s appointment had been manufactured by the left.

“Are Democrats trying to tell other Democrats that supporters of the U.S.-Israeli relationship aren’t welcome in leadership positions — and who is next?” said Representative Josh Gottheimer, a centrist Democrat from New Jersey and a staunch supporter of Israel. “Is this a new litmus test for committee chairs? Moskowitz is beyond qualified.”

He called the progressive outrage “selective” and politically misguided, noting that it was coming as many in the party are encouraging pro-Israel Democrats to swallow their concerns about Abdul El-Sayed, the nominee for Senate in Michigan who is a vocal critic of Israel.

“This election should be about affordability and Trump’s corruption, and they want to make it about Jews and Israel,” Mr. Gottheimer said.

The decision cheered center-leaning Democrats and some donors, who said it indicated that Mr. Jeffries would not allow the party to be taken over by the demands of the Democratic Socialists of America.

Mr. Moskowitz, on social media, expressly thanked Mr. Jeffries for giving him “this important responsibility to help lead Democrats policy in the Middle East.”