Former President Donald Trump and President Joe Biden have both clinched their respective nominations in the presidential race, but primary season is just getting started. The biggest state to watch tonight is in Ohio, where a closely contested GOP primary will decide which Republican faces off against Sen. Sherrod Brown in one of this fall’s biggest Senate races. Trump-endorsed businessman Bernie Moreno seems to have an edge in that contest over state Sen. Matt Dolan and Ohio Secretary of State Frank LaRose. Trump-aligned Republicans will be pulling for Moreno today — but so might Democrats, who see Moreno as an easier target to defeat in November.

Which wing of the GOP comes out ahead seems to be the theme of the day throughout the Buckeye State, where we’re also tracking a slew of competitive Republican primaries for U.S. House. Meanwhile, two incumbents in Illinois — Democratic Rep. Danny Davis and Republican Rep. Mike Bost — are looking to stave off tough primary challenges, while California will host a Super Tuesday rematch in a special election to decide who will fill former Speaker Kevin McCarthy’s seat in the House for the remainder of this year.

As for timing, we should start to see results come in shortly after polls close at 7:30 p.m. Eastern in Ohio and 8 p.m. Eastern in Illinois. As always, 538 analysts will be here bringing you the latest results and analysis throughout the evening. Thanks for joining us!

—Tia Yang, 538

The GOP primary for Senate in Ohio is, by leaps and bounds, the most expensive Republican primary race of the cycle — and the second-most expensive Senate primary overall this year (after California’s Senate contest). The three major Republican candidates and their allies have spent a combined $41.2 million through March 19.

The spending picture has largely been dominated by Dolan and Moreno, with LaRose, who is not personally wealthy like the other two, unable to keep pace. Dolan has spent $10.6 million on advertising while Moreno has spent $8.5 million. LaRose has not spent money on broadcast TV, cable, over-the-top/streaming or digital ads, according to data from AdImpact.

When it comes to outside spending, Dolan’s allies at the super PACs Buckeye Leadership Fund (which is largely funded by Dolan’s family) and Defend Ohio Values have spent $7 million and $1.7 million, respectively, bringing the pro-Dolan total to $19.3 million in spending.

Moreno’s supporters at the Club for Growth ($5.9 million), Buckeye Values PAC ($1.3 million) and Win It Back PAC ($823,000) — plus $3.3 million from a Democratic super PAC boosting Moreno because they believe he’ll be an easier general election opponent for Brown — bring the pro-Moreno squad’s total ad outlay to just under $20 million.

LaRose, who raised just $2.2 million through the end of February, is relying on support from his allied super PAC, Leadership for Ohio. That group has spent $5.4 million to boost his bid.

Ultimately, LaRose’s lack of access to significant personal funds hindered his ability to capitalize on the early name ID and polling advantage he had as a two-time statewide elected official. Dolan donated $9 million to his campaign out of his own pocket, and Moreno put $4.2 million of his own money into his campaign.

—Jacob Rubashkin, Inside Elections