WASHINGTON, D.C. — Total ad spending in the Ohio Senate race is now projected to reach more than $400 million, according to ad tracking firm AdImpact, making it by far the most expensive Senate race this cycle.

The spending comes as both parties see Ohio as key to take control of the Senate amid an increasingly tight Senate race landscape.

It comes down to the math: West Virginia is expected to elect a Republican to replace Sen. Joe Manchin, meaning Democrats must either hold both Ohio and Montana or flip Florida and Texas. If Brown loses in Ohio, Democrats would need to win all three other states, which currently are all leaning Republican in polls.

Republicans ramped up their spending in September, spending about $70 million on ads for Bernie Moreno, double Democrats’ spending of $35 million to support Sen. Sherrod Brown. The push followed Democrats outspending Republicans all summer. According to AdImpact, the trend is set to continue, with $77.6 million currently reserved for ads to boost Moreno and $67.2 million reserved for ads to boost Brown.

AFP Action, a super PAC that supports Republican candidates, reserved $10 million in ads across six battleground states, including in Ohio to support Moreno.

“AFP Action is leading the charge on the ground with grassroots voter outreach, from knocking nearly 600,000 doors to date and placing targeted ad buys that help reinforce the message our experienced canvassers are delivering at the door in face-to-face conversations. We are a 7-days-a-week operation through Election Day,” AFP Action Ohio senior adviser Donovan O’Neil wrote in a statement.

“So we're very involved in Ohio. There's no way I'm losing Ohio,” Sen. Gary Peters, D-Mich., who chairs the DSCC, said at a press event Sept. 26. “We're not done investing in Ohio. And it will take more money, but right now, you have a lot of outside groups that are dumping tens of millions of dollars against Sherrod, trying to prop up another highly flawed candidate.”

Recent polls show the race tightening, though Brown maintains a 3.7-point lead in the RealClearPolitics poll average.

The closeness of the race leaves both candidates vulnerable to any error that could eat into their support.

Moreno may have made such an error while giving remarks at a town hall in Warren County, Ohio on Sept. 20, in which he suggested older women should not care about abortion rights.

“It’s a little crazy, by the way, especially for women that are like past 50,” Moreno said at the event. “I’m thinking to myself, ‘I don’t think that’s an issue for you.’”

Moreno’s campaign responded in a statement that he was “making a tongue-in-cheek joke” and that he believes women also care about other issues, like the economy and crime.

But the comments drew criticism from both sides of the aisle. Former GOP presidential candidate Nikki Haley posted on X, “Are you trying to lose the election?”

Brown’s campaign held multiple campaign events focusing on the comments.

“I don't trust this Moreno to represent me and the citizens of Ohio on this issue with many others. So I'll be voting for Senator Brown this November,” Ed Dunn, a self-described Republican from Beavercreek, Ohio, said at a Brown campaign event Sept. 26 in Columbus.

Early voting starts in Ohio on Oct. 8.