Democratic voters in Illinois handed the party’s nominations for five open seats in the House of Representatives to candidates that included Evanston mayor Daniel Biss and Cook County commissioner Donna Miller, after heated and at times bitter campaigns that saw significant spending by outside groups, most controversially the American Israel Public Affairs Committee (Aipac).

The primaries acted as a test of the style of politics voters were looking for ahead of the midterm elections in November, when Democrats hope to regain control of Congress. All five districts are heavily Democratic, making the primary victors favorites to triumph in the general elections.

Biss, the mayor of Evanston, Illinois, won the race to replace retiring longtime Representative Jan Schakowsky in Illinois’s ninth congressional district. The race in Chicago’s north suburbs was one of the most closely fought primaries, with 15 candidates vying for the nomination.

The contest, which turned heavily on the party’s divisions over Israel, included Kat Abughazaleh, a 26-year-old and former researcher for the left-wing media organization, Media Matters, and Laura Fine, a state senator. Fine drew support from Elect Chicago Women, an outside group reportedly tied to the pro-Israel lobbying group.

Alexandra Rojas, executive director of Justice Democrats, the left-wing group that works to defeat “corporate Democrats” and had backed Abughazaleh, called the results a “massive loss for Aipac”.

“No amount of shell PAC’s or covert funding can hide their toxicity from Democratic voters, their monopoly over this Party’s agenda is coming to an end,” she said.

The Progressive Change Campaign Committee celebrating Biss’s nomination as proof “that voters can see through corporate-funded ads that package corporate-backed candidates as bold economic populists”.

Aipac, which had not formally acknowledged its role in trying to defeat a string of candidates critical of Israel, said on Tuesday that it was “proud to have helped defeat” Abughazaleh, a first-time candidate and Palestinian American who frequently criticized the group and said Israel’s military operations in Gaza amounted to a genocide.

“A great night for the pro-Israel community and a terrible night for anti-Israel candidates,” Aipac wrote in a post on X.

Ten candidates were standing to replace congresswoman Robin Kelly in the second congressional district, after she opted to retire from the House and instead run for the US Senate seat vacated by Dick Durbin. But it was Miller, the Cook County commissioner and former health care consultant, who prevailed, AP reported.

The majority Black district covers South Chicago and nearby suburbs, and has been represented by African American lawmakers for decades. Jesse Jackson Jr, the son of the late Jesse Jackson, was hoping for a comeback to the district after he resigned in 2012 amid health issues and an investigation into misuse of campaign funds, for which he served time in prison.

But Miller had the cash advantage, though the Chicago Tribune has found that more than half of her donors had previously contributed to the American Israel Public Affairs Committee or affiliated groups. Miller nonetheless sought to distance herself from Aipac.

In the seventh district on Chicago’s west side, La Shawn Ford won the nomination to replace Danny Davis, who represented the area since 1997. She prevailed against a dozen candidates, with the AIPAC-affiliated United Democracy Project running ads in support of Chicago city treasurer, Melissa Conyears-Ervin.

Melissa Bean, a moderate former congresswoman who had lost re-election to a Republican in 2010, emerged from an eight-way contest to win the primary to replace congressman Raja Krishnamoorthi, in the eighth congressional district in Chicago’s western suburbs. In the final days of the campaign, Bean had received a rush of support from Elect Chicago Women, to help fend off a progressive rival, progressive rival, Junaid Ahmed.

The race to replace longtime congressman Jesús “Chuy” García in the majority-Hispanic fourth district attracted considerable controversy, when García opted to announce his retirement at the same time that his chief of staff, Patty García, jumped into the race. That effectively left voters with a single choice for the Democratic primary, prompting moderate Washington congresswoman Marie Gluesenkamp Perez to successfully propose a House resolution condemning García for “undermining the process of a free and fair election”.

As expected, Patty García, who has no relation to the congressman, won that primary, according to AP.

“Together, we’re going to abolish ICE, build a humane immigration system with a real pathway to citizenship, and put an end to the terror being visited on our communities,” Patty García said in a statement, declaring victory on Tuesday night, adding: “And we’re going to hold Trump accountable.”