On Jan. 6, 2021, shortly after a violent mob of then-President Donald Trump’s supporters attacked the U.S. Capitol, newly sworn-in Rep. Mary Miller voted against certifying election results in Arizona and Pennsylvania for Joe Biden. Her fellow Illinois Republican, five-term Rep. Rodney Davis, voted the opposite way. 

The two didn’t anticipate it then, but after their state’s loss of a House seat in the congressional reapportionment process, they find themselves running against each other in a contentious, multimillion-dollar primary that will end one of their Capitol Hill careers.  

Illinois’ new congressional boundaries not only put Miller and Davis together in the heavily GOP 15th District — which covers the state’s largely rural eastern and southern enclaves — it also resulted in a pair of Democrats, freshman Rep. Marie Newman and two-term Rep. Sean Casten, running against each other for the Chicago-area 6th District nomination. They, too, have diverged on some high-profile, controversial matters, including legislation to fund an Israeli missile defense system, according to a CQ Roll Call analysis of their votes this 117th Congress.

The two pairs of lawmakers have spent a year and a half voting side by side, and, not surprisingly, the Democrats tended to stick together on most issues, as did the Republicans. But their splits reveal the fissures within their respective parties and have fueled outside spending and potentially pivotal endorsements. The candidates who emerge victorious after Tuesday’s primaries may offer clues about how voters are seeking to settle divisions from within. 

Democrats divide 

Newman, who won a 2020 primary against then-Rep. Dan Lipinski, one of the last anti-abortion rights Democrats in Congress, continues to highlight her support for the issue, an especially important one after last week’s Supreme Court decision overturning Roe v. Wade. But Casten, unlike Lipinski, has a record of supporting abortion rights, too. Planned Parenthood has endorsed both Democrats.

Casten and Newman have taken opposite positions on 47 votes this Congress, according to the CQ Roll Call analysis, out of a total of 723 roll call votes cast through mid-June. One of those was the measure to fund the Israeli military system known as Iron Dome, something that split other Democrats at the time. 

All told, Casten voted in line with the Biden administration’s preferred outcome on legislation 98.7 percent of the time, while Newman voted with Biden 100 percent of the time. Casten voted with Democrats on 99.4 percent of votes that split along party lines, Newman 100 percent. 

Support for Israel is a burgeoning dividing line among Democrats and has become a flashpoint in other primaries.

Newman said that, in her view, the United States had already fulfilled its funding commitment for Iron Dome. She called the defense system a “great thing and we’re so glad that that helps them keep safe.” 

“We committed to a very specific amount of money which we then gave to them this past year, and we made our full commitment,” she said in a recent interview. “A couple months later, Israel came back and said, ‘Hey, can we have $1 billion?’ And I have to tell you, I’m of the mindset in my district, very definitely. … We’re a frugal bunch.” 

The biggest outside spender in the 6th District has been the pro-Israel DMFI PAC, which invested more than $500,000, nearly all going to opposition to Newman. 

Her Iron Dome vote was the “coup de grâce,” said Mark Mellman, DMFI PAC’s chairman. “She has done everything one possibly could to elicit the opposition of everyone who is pro-Israel,” he added.  

Casten has outraised Newman, hauling in $3.2 million this cycle to her $1.5 million.

Apart from their votes, Newman has faced ethics issues during her first term. She says those matters are a nonissue on the trail. “Literally, I have knocked on over 7,000 doors, we’ve had 150 meet and greets and it’s never been asked about,” she said. “It has been deemed a zero merit case. We have moved on. Everybody has moved on.”

The House Ethics Committee was still looking into the matter as of earlier this year. 

Casten, meanwhile, voted against some bills whose underlying policy his campaign says he actually supports, including one this year that set out a military sexual trauma examination review, something Newman said she strongly supported. Jacob Vurpillat, Casten’s deputy campaign manager, said the congressman declined an interview request because of the recent death of his daughter but explained that he has a policy of voting against any bills sponsored by lawmakers who objected to the 2020 presidential election results. Texas Republican Rep. Troy Nehls sponsored that bill. 

Battle for the GOP

The split over the 2020 presidential election was a key dividing line early on for Davis and Miller. Trump endorsed Miller and campaigned for her over the weekend with a rally in Mendon, Ill. 

Miller has already cut an ad featuring Trump and calling Davis a “RINO,” or Republican in name only. Miller’s ad did not include her referring, as she did at the rally with Trump, to the recent Supreme Court abortion ruling as a win for “white life.” Her campaign, which did not respond to an interview request, said she had misspoken. Davis’ campaign reminded voters that in her earliest days in office, Miller apologized for comments about Adolf Hitler. 

Much of the messaging in the race has been dominated by outside groups, including the Club for Growth, which has disclosed millions in support of Miller and attack ads against Davis. Outside interests had invested almost $12 million on the primary, showing the potential import it holds in the future of the GOP. That money eclipses what both candidates have hauled in this cycle: $3.5 million for Davis and $1.5 million for Miller. 

Davis, in an interview, said that “nobody’s really talking about” his Jan. 6 votes on the campaign trail. “I did what I thought was my constitutional duty under the 12th Amendment,” he added. 

The leading Republican on the House Administration Committee, Davis has touted his support for Trump’s agenda, even after the former president announced his rally, and the congressman said that should he gain the panel’s gavel after the midterm elections, he would probe the Jan. 6 committee’s work.  

During the four years of the Trump administration, Davis voted in line with the president’s stated policy on legislation 89.8 percent of the time, below the average for all Republicans of 92.1 percent presidential support. 

Davis and Miller’s disagreements on legislation also included votes on the Violence Against Women Act reauthorization. Davis voted yes, while Miller voted no. They’ve voted opposite each other on 152 votes, out of a total of 723 roll call votes cast so far this Congress. 

On votes that broke along party lines, Miller supported the GOP position 98.3 percent of the time, while Davis backed his party on 87.5 percent. During the Biden administration, Davis has voted in favor of the Democratic administration’s public position 24.6 percent of the time to Miller’s 6.6 percent. His more moderate voting record may speak to his past running in a swing district. Davis survived the 2018 blue wave in a close reelection. 

Though Miller has the support of Trump, Davis’ endorsers include the U.S. Chamber of Commerce. Davis said on a number of issues, the two agree. 

“We’re both 100 percent pro-life. We’re both standing up for the Second Amendment,” he said. “And those are the things that a lot of voters want to talk about.”

He said he has proven himself capable of turning policy ideas into law, noting his work on past farm bills and a provision in the CARES Act that sought to encourage employers to help pay down their workers’ student debt.

“In the end, I talk about the difference between us is experience and the ability to govern,” he said.

Ryan Kelly contributed to this report.