JEFFERSON CITY, Mo. (AP) — St. Louis businessman John Brunner has already poured at least $1 million into his Republican quest to challenge Democratic U.S. Sen. Claire McCaskill, and new documents show Brunner has a lot more where that came from.

Brunner and his wife, Jan, have assets worth at least $26 million and perhaps as much as $108 million, according to a personal financial report provided Friday to The Associated Press. That means Brunner would be one of the nation's richest senators, if elected. And it could provide ammunition to political opponents if they want to portray Brunner as out of touch with the average American — a story line already being used against Republican presidential candidate Mitt Romney.

The finance report filed this week with the U.S. Senate shows that much of Brunner's wealth stems from his ownership stake in Vi-Jon Inc., a company founded a century ago by his grandparents that now produces personal health care products such as Germ-X hand sanitizer. Brunner launched his campaign last October while standing in front of boxes of nail polish remover and petroleum jelly at the company's distribution center in St. Charles.

Although he stepped down as chairman of the company before entering the Senate race, Brunner remains on the board of directors, still owns nearly one-fifth of Vi-Jon's holding company and was paid a salary of $372,000 from Jan. 1, 2011, through Jan. 30, 2012, according to the financial documents.

Brunner's ownership share of VJCS Holdings Inc. is worth between $14 million and $70 million, according to the financial report.

Those figures vary so widely because the U.S. Senate only requires candidates to categorize their assets in general dollar ranges. For example, the federal forms have categories for items valued between $1 million and $5 million or between $5 million and $25 million.

A Brunner campaign spokesman said his wealth highlights a "success story" that "defines the American Dream."

"While his personal success is noteworthy, the real legacy of John Brunner's success is that he was able, through hard work, to grow a small family manufacturing business from 80 to 1,400 employees, and in the process create opportunities for success for hundreds of other families in his own community," campaign spokesman Todd Abrajano said in an emailed statement.

Yet Brunner's campaign is also aware of the potential political sensitivities regarding his wealth. A campaign attorney went over the finance report page-by-page with the AP on Friday to explain each item.

The release of Brunner's finance report comes as Romney has been taking criticism from Republican presidential rival Newt Gingrich — and from Democrats — over how the former Massachusetts governor acquired part of his considerable wealth. Earlier last month, for example, Gingrich criticized Romney's former private equity firm, Bain Capital, as "exploitive" of the companies in which it invested. Last week, Romney's wealth again was in the headlines, as he acknowledged that his 2011 financial disclosure report had failed to list an unknown amount of investment income from various sources, including a Swiss bank account.

"The exposure of Romney's wealth — and the split within the Republican Party and between Republicans and Democrats — makes Brunner vulnerable as 'someone who's not like us,'" said George Connor, head of the political science department at Missouri State University.

But that may be true only if Brunner's Republican rivals for the seat — U.S. Rep. Todd Akin and former state Treasurer Sarah Steelman — try to follow Gingrich's example by making an issue of Brunner's riches, Connor said.

McCaskill would have little room for criticism. The Center for Responsive Politics, which runs the website opensecrets.org, ranks McCaskill as the 11th wealthiest senator. Brunner's wealth would put him ahead of McCaskill, perhaps around eighth.

Among other things, his report shows that he owns a Raytheon King Air 350 airplane worth between $1 million and $5 million and VJCS Holdings also owns a plane. The documents show that Brunner owns a condominium in Cambridge, Mass., which his campaign said he bought for his sister who is in poor health.

The Senate does not require candidates to list their personal residences. But Brunner's campaign confirmed he owns three homes — one in St. Louis, another in Michigan and a third in the Cayman Islands.

Brunner, who is making his first campaign for office, has been running on his experience in creating jobs and calling for change in Washington.

"The wealth issue is going to undercut the utility of the, 'I'm an outsider kind of person,'" Connor said.

John Brunner

Mo. candidate would be among richest in US Senate