For many voters in Illinois, nothing appeared overtly suspicious in the 30-second election advertisement that aired in mid-March.

The video starts with a burst of cheerful music, and a narrator praises congressional candidate Bushra Amiwala as a fighter for “real economic justice” and “the real deal”.

But the video was not part of a genuine effort to get Amiwala elected to the United States House of Representatives. And the candidate quickly disavowed it.

Instead, public records reviewed by Al Jazeera now show the commercial was paid for by a political action committee (PAC) associated with the largest pro-Israel lobby group in the US.

Funding for the advertisement came from the American Israel Public Affairs Committee (AIPAC), which has been pumping tens of millions of dollars into election campaigns in a push to sink candidates critical of Israel.

With the midterm primary season in full swing, advocates say AIPAC is placing its thumb on the scale in many congressional races. Its tactics, they argue, undermine election transparency.

“Every cycle, AIPAC shows just how broken our democracy is and how corrupt our political finance system is,” said Usamah Andrabi, a spokesperson at Justice Democrats, a progressive group.

“Every cycle, they are at the forefront of exploiting those gaps for their right-wing donors and at the expense of voters.”

Shell PACs

In Illinois, the advertisement aimed to boost Amiwala in order to syphon off votes from more viable progressive candidates — namely, Palestinian American activist Kat Abughazaleh, who ended up losing the race narrowly.

While the Chicago Progressive Partnership — the group whose name appeared on the Amiwala advertisement — was widely believed to be linked to AIPAC, it did not have to reveal the source of its funding until after the elections, which took place in March.

Now that the vote is over, Federal Election Commission receipts show that the sole funder of Chicago Progressive Partnership was Elect Chicago Women (ECW), another PAC. It contributed $1m to the partnership.

In turn, ECW had raised more than $4m from United Democracy Project (UDP), the election arm of AIPAC, and another $1m from investor Blair Frank, one of UDP’s largest donors.

AIPAC also contributed $1.3m to a third PAC, Affordable Chicago Now, in what critics call an effort to conceal its spending in Illinois.

Palestinian rights advocates say this use of “shell PACs” is evidence of how the pro-Israel group has become “toxic” among the US electorate. They argue AIPAC has taken a Russian doll approach — hiding its spending by funnelling funds from one PAC to another — to hide its involvement in primary races.

“They are so unpopular amongst the Democratic Party that they have to hide themselves,” Andrabi told Al Jazeera. “We have to keep exposing them and looking under every rock to see whether or not this shell PAC or that shell PAC is funded by AIPAC.”

Part of the backlash has come from broader public disillusionment with Israel-backed policies, including the joint US-Israeli war against Iran and the genocidal assault on Gaza, which AIPAC supports.

As a result, Israel has been rapidly losing support among the US public.

Just this week, The New York Times and Siena College released a survey showing that 37 percent of US voters now sympathise with Palestinians, while 35 percent sympathise with Israelis.

That number was even higher among Democratic respondents, 57 percent of whom felt greater sympathy for the Palestinians.

The Pew Research Center suggested an even stronger left-wing backlash. Its survey earlier this year found 80 percent of Democratic respondents said they have unfavourable views of Israel.

For many voters, AIPAC has come to symbolise the oversized influence of campaign spending in US politics, turning the group into a pariah — especially among Democrats.

Some politicians who previously received support from the group are now disavowing it.

Omar Shakir, the executive director of the US-based rights group DAWN, said AIPAC’s use of shell groups is a reflection of that growing repudiation.

Routing funds “through layered PAC structures designed to obscure where the money originates reflects weakness, not strength”, he told Al Jazeera.

“They can’t defend Israel’s genocide, apartheid and ethnic cleansing, so they’re rigging the system outside of public view.”

Lack of transparency

A 2010 US Supreme Court ruling has allowed corporations and advocacy groups to spend unlimited amounts of money in elections, as long as they do not directly coordinate with the campaigns they are backing.

In many cases, PACs do not have to list all of their donors until after the elections. Some nonprofits that influence elections — known as dark money groups — do not have to reveal their donors at all. And there are few rules about messaging.

Experts say AIPAC has exploited these loopholes to advance its goals. But the lack of transparency is causing confusion in many races.

For example, in a competitive Democratic primary in Pennsylvania, candidate Ala Stanford insisted that she did not receive AIPAC money.

But the largest spender in the race was 314 Action Fund, a PAC that backs Democratic scientists, which supported Stanford, who is a paediatric surgeon.

AIPAC transferred $1m to 314 Action Fund in the last election cycle in 2024, but the extent of the group’s involvement in the Pennsylvania race remains unclear.

Progressive state legislator Chris Rabb, who has condemned Israel’s atrocities in Gaza as a genocide, ended up winning that primary on Tuesday.

In Kentucky, meanwhile, AIPAC and other pro-Israel groups helped defeat Congressman Thomas Massie, a rare Republican critic of President Donald Trump.

It was the most expensive House primary in US history, but the names of the donors of the PAC that spent the most money in that race have not been fully made public.

While it may be difficult to prove AIPAC’s spending in some races, Andrabi said it is not enough for candidates to merely distance themselves from the pro-Israel group.

“We know that AIPAC does not throw money at candidates unless those candidates will rubber-stamp their agenda in Washington,” he said.

“So it’s not just about what they say and whether or not they deny they have AIPAC support. Let’s ask them what policies they will support in Congress. Will they support an arms embargo against Israel? Will they call a genocide a genocide? Will they stop all funding to the Israeli government and military? That’s a good litmus test for us to do.”

AIPAC’s connections

Beyond its work with UDP and associated PACs, AIPAC has encouraged individual donors to contribute to the campaigns of 361 legislators, including Republican House Speaker Mike Johnson and Democratic Minority Leader Hakeem Jeffries.

The contingency of AIPAC-backed members of Congress spans the ideological spectrum, from prominent liberals like Ted Lieu to far-right, anti-Muslim figures, including Randy Fine.

In his 2020 memoir, former President Barack Obama acknowledged AIPAC’s influence in Washington, saying that politicians were worried about “crossing” the lobby group.

“Those who criticized Israeli policy too loudly risked being tagged as ‘anti-Israel’ (and possibly anti-Semitic) and confronted with a well-funded opponent in the next election,” Obama wrote.

AIPAC did not respond to Al Jazeera’s request for comment by the time of publication.

Despite its well-documented clout, AIPAC’s organisational structure remains murky, as well as its spending.

On Wednesday, DAWN, the rights group, released a report that relied on LinkedIn disclosures to track the group’s current and former staff members and their professional connections.

It found that many people who worked for AIPAC also held jobs with the US and Israeli governments.

“DAWN’s analysis shows that 66 former AIPAC staffers currently work in the US government, from Congress to the White House to various branches of the military; nearly two dozen current AIPAC staffers previously worked in US government bodies,” the report said.

“The personal and professional relationships that result from this type of revolving door form the backbone of political influence in Washington, which is indicated in the hundreds of professional connections between AIPAC staffers and US federal and state employees.”

The group called on AIPAC to make public the names of the people who lead and work for the group.

“AIPAC should publish, at minimum, a current leadership page on its official website,” DAWN said.

“The page should identify AIPAC’s officers, board of directors, senior staff, and department heads with photos and biographies. AIPAC should also publish an organizational chart showing how the institution is structured. This is the floor that comparable tax-exempt nonprofits already meet.”

It noted that most leading advocacy groups, including DAWN itself, publish the names and bios of their staff and board members.

Because of AIPAC’s tax-exempt status as a nonprofit, Shakir said taxpayers “effectively subsidise” the pro-Israel group.

“They deserve to know how AIPAC works to shape US policy to the Middle East and who works for it,” he told Al Jazeera.