Millionaire candidates and billionaire investors are pooling their resources to compete for vacant US Senate seats in Ohio and Pennsylvania.

Mike Gibbons, an Ohio investment banker, has contributed over $17 million to his own campaign.

Three other wealthy candidates in the Ohio race have lent or contributed a total of $14 million to their campaigns: state Sen. Matt Dolan, whose family owns the Cleveland Guardians baseball team; former Ohio Republican Chair Jane Timken, whose husband's family founded the steel giant Timken Co.; and "Hillbilly Elegy" author JD Vance.

In Pennsylvania, Mehmet Oz, a heart surgeon with a TV show, former hedge fund CEO David McCormick, and former real estate investment company CEO Carla Sands have all contributed more than $20 million to their respective campaigns.

Billionaire computer investor and PayPal co-founder Peter Thiel has given millions to a super PAC supporting Vance, while hedge fund billionaire Ken Griffin has contributed millions to McCormick.

Sands, Oz, and McCormick all claim to be worth tens of millions, if not hundreds of millions, of dollars and to own homes around the country, according to their financial filings.

The infusion of cash into the primaries in Ohio and Pennsylvania demonstrates the significance of the two Senate seats, which may help determine party control of the chamber in November. 

According to Sheila Krumholz, executive director of OpenSecrets, a research group that tracks campaign spending, wealthy candidates are choosing self-funding due to the lack of limitation on personal contributions. 

“The massive spending by super PACs and outside groups with anonymous sources means that candidates really can never stop fundraising," Krumholz stated, adding that “they can never have enough money, so self-funded candidates have that built-in advantage. You’re not only raising money to fight an opponent or opponents, you need money to fend off attacks that could come from anywhere, at any moment, in any amount of money.”

Mandel, the state’s former treasurer, is the only candidate who has not given himself a personal contribution. 

Kathy Barnette, a Republican candidate allied with pro-Trump ultra-conservatives, has said that GOP has a habit of electing the "richest person".

Barnette questioned "how has that served us? Picking the richest person, just because they are the richest person," asking voters, "how many of them in the past two years have stood up for you?"

Additionally, Terry Casey, a Republican strategist in Ohio, says the influx of personal funding can be alarming to voters. “So there’s an argument that if you’re self-funding, maybe you’re less tainted, but then it raises the question of, ‘Is this an ego or vanity campaign?’”