Illinois and Ohio primaries 2024: Trump-backed Senate candidate prevails in Ohio primary

538 tracked key House and Senate races, including a California special election.

November’s presidential matchup may be set, but Democrats and Republicans still need to decide who will run in hundreds of downballot races (e.g., for Senate and House) this fall. A batch of these contests were decided on Tuesday, March 19.

Tuesday was primary day in Ohio and Illinois, and in the biggest contest of the day, Republicans chose former President Donald Trump's endorsee Bernie Moreno as their candidate in Ohio’s U.S. Senate race. It was a good night for other Trump endorsees too, as Derek Merrin prevailed in the GOP primary for Ohio's 9th Congressional District, while incumbent Mike Bost is leading his challenger in Illinois's 12th District, as of early Wednesday morning. Plus, a special election in California could have immediate implications for House Republicans’ razor-thin majority.

538 reporters and contributors broke down the election results as they came in with live updates, analysis and commentary. Read our full live blog below.


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There technically are still presidential primaries tonight

You didn’t think we’d forget, did you, dear reader? In Florida, Illinois and Ohio, ABC News is projecting that Trump and Biden have won their primaries.

—Mary Radcliffe, 538


Answer: It's Trump's party regardless

Pretty much nothing that happens tonight will alter the view that the GOP is unmistakably Trump's party. Even if a Trump endorsee were to lose, the party is clearly behind Trump and most Republican candidates have aligned themselves with him. That's the recipe to generally appeal to GOP voters. It's true that Dolan could conceivably win the Republican Senate primary in Ohio, but if he does, it'll likely be with a small plurality around 40 percent. The majority of the party will be with the Trump-endorsed candidate (Moreno) or the one who has more closely aligned himself with Trump (LaRose) in what looks to have been a failed effort to win the primary.

—Geoffrey Skelley, 538


Answer: So far, Trump’s Ohio endorsees haven’t stood out much

I've been keeping a close eye on Trump's Truth Social account, and one thing I noticed this time around is that his endorsement of Merrin in Ohio's 9th came fairly late in the game. He endorsed Moreno on December 19, but he didn't issue an endorsement in the 9th until yesterday afternoon!

Now, there may be reasons Trump waited to make an endorsement in the race. A key Trump ally in the state, Rep. Jim Jordan, had already endorsed Riedel, so maybe Trump was trying not to get on his bad side. But the fact that he waited so long will almost certainly diminish the impact of the endorsement with voters.

When it comes to the Senate race, Tia, the fact that it's as close as it appears to be even given Trump's endorsement may already tell us something about his impact in these sorts of races. The non-MAGA establishment obviously still holds significant sway among voters, at least in Ohio.

All that is a long-winded way of saying that I'm not sure Trump is showing much strength with his Ohio endorsements. The races are very close, so whatever he's doing hasn't seemed to impact the electorate as much as he would probably hope to.

—Mary Radcliffe, 538


Answer: A lot and a little

The result in Ohio's Senate primary is probably the most germane to Trump's influence in the party (or at least among the primary electorate) because Dolan alone has sometimes distanced himself from Trump. Now, he's decidedly less Trump-skeptical this time around than he was in 2022, but he's still the closest thing to a more pre-Trump traditional politician in any of these races. Moreno, meanwhile, was an also-ran until Trump picked him as his champion. (He flunked out of the 2022 race despite self-funding.) If Trump can push him to a win like he did J.D. Vance two years ago, that's a sign of strength. In the other contests, I'm not sure there's much to be gleaned. Mike Bost and Darren Bailey are both running very Trump-heavy campaigns. Bailey wasn't endorsed by Trump, but still features him in his ads! Not sure it says much if that's a winning message. And in Ohio's 9th, Merrin may have the endorsement, but Riedel has been working overtime to show his loyalty after those embarrassing clips leaked. Plus, Merrin's only had the endorsement for a few days, and it hasn't featured in any TV ads in the race.

—Jacob Rubashkin, Inside Elections