CHICAGO — A bitter intraparty battle drew to a close Tuesday as Democratic primary voters went to the polls to decide who would be their choice to replace retiring U.S. Sen. Dick Durbin.

The race for Illinois’ first open Senate seat in 16 years — fueled by tens of millions of dollars in campaign and outside spending — narrowed to three leading contenders in a crowded field: U.S. Reps. Raja Krishnamoorthi of Schaumburg and Robin Kelly of Lynwood and Lt. Gov. Juliana Stratton of Chicago.

While the top candidates largely aligned on many issues, the campaign exposed fissures within the state’s dominant political party, including how far to go in overhauling the federal immigration system in the wake of President Donald Trump’s militarized enforcement crackdowns and how aggressively Democrats should embrace economic populism.

With Gov. JB Pritzker backing Stratton, his two-time running mate, the Senate primary also served as a test of the billionaire Democrat’s broader political influence as he seeks a third term in November and considers a potential 2028 presidential bid. Pritzker, unopposed in Tuesday’s primary for governor, contributed at least $5 million to an ostensibly independent super political action committee, Illinois Future, which reported spending roughly $12.2 million to boost Stratton’s campaign.

Krishnamoorthi, meanwhile, amassed about $30.5 million in his campaign fund, money he had stockpiled for years while representing a safely Democratic suburban district for five terms and preparing for a Senate run. The total ranked second-largest among federal candidates nationally this year, allowing him to begin running TV commercials across the state in July, months before his rivals.

As Election Day neared and those funds dwindled, outside political committees funded at least in part by Krishnamoorthi supporters poured more than $11.6 million into the race. The vast majority was spent by a pro-cryptocurrency PAC, Fairshake, on ads attacking Stratton, but some was also spent on ads supporting Krishnamoorthi and, in an effort to drive Black voters away from Stratton, boosting Kelly.

A seven-term lawmaker and the most experienced of the top candidates, Kelly struggled to break through the bickering, a dynamic her campaign referenced in a closing commercial in which she knocked over a television playing dueling ads featuring Stratton and Krishnamoorthi slamming each other. Pritzker’s full-throated support for Stratton, which some of Kelly’s backers in the Congressional Black Caucus decried as heavy-handed, revived past tensions over the governor’s maneuvers four years ago to oust the south suburban congresswoman as head of the state Democratic Party.

Also seeking the Democratic nomination were Kevin Ryan, Steve Botsford Jr., Bryan Maxwell, Jonathan Dean, Sean Brown, Awisi Bustos and Christopher Swann.

In heavily Democratic Illinois, where the last Republican elected to the Senate was Mark Kirk in 2010 and the GOP’s last statewide victory came in 2014, the Democratic nominee is the prohibitive favorite in November to replace Durbin following a 30-year tenure in the Senate.

The field of candidates hoping to chart a new course for beleaguered Illinois Republicans included former state GOP Chair Don Tracy of Springfield, whose tenure leading the party came to an end in 2024 amid squabbling among various factions; attorney Jeannie Evans, a first-time candidate; Casey Chlebek, who unsuccessfully sought the GOP Senate nomination in 2020 and 2022; Pamela Denise Long; Jimmy Lee Tillman II; and R. Cary Capparelli.

Unlike in the Democratic contest, the Republican Senate primary drew little outside spending.

As voters cast ballots in person and deposited mail ballots in drop boxes, Kelly, Krishnamoorthi and Stratton, all of whom voted ahead of Election Day, made final campaign stops before gathering with supporters in Chicago to watch the returns: Kelly on the South Side, Krishnamoorthi on the Near North Side and Stratton on the West Side.

While disputes over campaign contributions and spending from outside backers dominated debates and negative ads, the three leading candidates also staked out differing positions on several issues, most notably how to push back on the aggressive, sometimes deadly tactics of U.S. Immigration and Customs Enforcement and Border Patrol under Trump.

Embracing a slogan associated with the party’s more progressive wing, Stratton called to “abolish ICE,” without offering a thorough explanation of what would replace the agency. Krishnamoorthi said he wanted to “abolish Trump’s ICE,” a position he repeatedly noted he shares with Pritzker. Kelly, who introduced articles of impeachment against now-former Homeland Security Secretary Kristi Noem, called for a complete overhaul of the Cabinet-level agency.

Economic concerns also loomed over the campaign as Democrats nationally sought to turn affordability issues that helped propel Trump back to the White House against the president and his party in the midterm elections. All three top candidates supported raising the $7.25-per-hour federal minimum wage. Stratton called for an immediate increase to $25 an hour — a position her opponents, who supported a gradual increase to $17 per hour, said reflected naivety and a lack of Washington experience.

The candidates also all called for changes to make health care more affordable and accessible, with Stratton and Kelly backing the so-called Medicare for all proposal and Krishnamoorthi favoring more immediate steps to shore up coverage under the Affordable Care Act.

Trump’s decision to go to war with Iran in late February thrust a new issue into the final weeks of the campaign, but it was one that saw little divergence among the candidates. All argued that it was an illegal action because Congress did not give authorization.

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