The US’s most powerful pro-Israel lobby group is pouring millions of dollars into influencing Democratic congressional primary races to counter growing support for the Palestinian cause within the party, including elections today in Pennsylvania and North Carolina.

The American Israel Public Affairs Committee’s money is focused on blocking female candidates who, if elected, are likely to align with “the squad” of progressive members of congress who have been critical of Israel.

But it is funneled through a group, the United Democracy Project (UDP), that avoids mention of its creation by Aipac and seeks to decide elections by funding campaign messages about issues other than Israel.

The UDP has thrown $2.3m in to Tuesday’s Democratic primary race for an open congressional seat in Pennsylvania – one of a handful of contests targeted by the group where a leading candidate is overtly sympathetic to the Palestinians.

The money has mostly been spent in support of a former Republican congressional staffer turned Democrat, Steve Irwin, in an attempt to block a progressive state representative, Summer Lee, who is leading in opinion polls in the solidly Democratic district which includes Pittsburgh.

Lee has spoken in support of setting conditions for the US’s considerable aid to Israel, has accused Israel of “atrocities” in Gaza, and has drawn parallels between Israeli actions and the shooting of young black men in the US. She is endorsed by Representatives Alexandria Ocasio-Cortez, Ilhan Omar and Rashida Tlaib, members of “the squad” who support the Palestinian cause.

Irwin has defended Israeli government policies and questioned whether Lee has “a strong conviction that Israel has a right to exist”.

The UDP has also spent $2m in support of North Carolina state senator Valeria Foushee in today’s Democratic primary in an attempt to block Nida Allam, the political director of Senator Bernie Sanders’s 2016 presidential campaign and the first Muslim American woman to hold elected office in North Carolina. Allam has participated in pro-Palestinian rallies and has been endorsed by members of the squad. She has also spoken out against antisemitism.

Aipac launched the UDP in December as a super political action committee, or Super Pac, which is permitted to spend without restriction in support of candidates but cannot make direct donations to campaigns.

The lobby group’s move into financial support for political campaigns for the first time in its 70 year history was prompted by alarm in Washington and Israel at the erosion of longstanding bipartisan support for the Jewish state in the US.

Opinion polls show younger Democrats are growing more critical of Israel, including American Jews, and that there is rising support for the Boycott, Sanctions and Divest (BDS) movement.

Israel is also concerned by the breaking of a longstanding taboo on comparing Israel’s domination of the Palestinians to apartheid South Africa after the publication of a series of international and Israeli human rights groups reports accusing Israel of practicing a form of apartheid.

The UDP has also spent $1.2m to protect the Texas Democratic congressman, Henry Cuellar, who faces a run-off later next week against Jessica Cisneros, a 28-year-old immigration lawyer who has spoken in support of the Palestinians and is endorsed by members of the squad.

Cuellar is described as an ally by Aipac and co-founded the Congressional Caucus for the Advancement of Torah Values to combat “anti-Israel bigotry”.

After Amnesty International joined other human rights groups in accusing Israel of imposing apartheid, Cuellar accused the group of endangering Jews. “Israel is not an apartheid state. Full stop. These inaccuracies incite antisemitic behavior against the Jewish people,” he tweeted.

A smaller and more liberal pro-Israel group, J-Street, has spent hundreds of thousands of dollars in support of Cisneros, saying she is committed to a more just solution to the conflict with the Palestinians.

J-Street’s spokesperson, Logan Bayroff, accused Aipac of being a Republican front organisation that strongly supported Donald Trump, and of attempting to intimidate candidates into avoiding criticism of Israel by implicitly threatening to fund campaigns against them.

“Aipac are taking all this money from Republican donors, and they’re obfuscating the fact that they’re a very Republican-aligned organisation while trying to persuade Democratic voters who they should support,” he said.

“The United Democracy Project sounds innocuous and the advertising that they’re running in these districts is about healthcare and reproductive rights and things that have nothing to do with Israel. Which makes sense because those are the things that decide elections, not Israel. But the reason that they’re aligning with certain candidates is because they are more aligned with their more hawkish positions on Israel, and because they fear that other candidates will be more progressive and aligned with the Palestinians.”

A UDP spokesman, Patrick Dorton, said the group was doing no more than running legitimate political advertising. “All we are doing is talking about candidate’s public record and that is something voters deserve to know,” he said.

Dorton said the group will be funding more campaigns.

“Our goal is to build the broadest bipartisan coalition in congress that supports the US-Israel relationship. We are proud to support pro-Israel progressive candidates including women of color,” he said. “We are looking at 10 to 15 other races where there is a pro-Israel candidate and a candidate that, if elected, would undermine the US-Israel relationship.”

Earlier this year, Aipac was accused by other leading supporters of Israel of being “morally bankrupt” and of putting Israel’s interests ahead of American democracy after it launched a separate political action committee that endorsed 37 Republicans candidates who voted against certifying Biden’s victory after the 6 January 2021 storming of the Capitol.

Aipac said that it supports politicians from both parties who will “advance the US-Israel relationship.

“It requires bipartisan support in Congress to adopt legislation that would advance that relationship. Consequently, we support members from both parties in their election races. In addition to the Republicans we have supported, we have made contributions to over 120 House Democrats, including half of the Congressional Black Caucus, half of the House Progressive Caucus, and the top Democratic leaders in the House,” Aipac said in a statement.