– Wealth has its disadvantages, at least when running for Congress.

In Minnesota's Eighth Congressional District, Republican Stewart Mills III is hoping to buck a trend that breaks against the well-heeled: Self-funded congressional candidates lose far more often than they win.

Millionaire congressional candidates who contributed at least a half-million dollars to their own campaigns won just 15 percent of House and Senate races between 2002 and 2012, according to the nonpartisan Center for Responsive Politics, an independent research group that tracks money in politics.

Personally bankrolling a congressional run is a gambit fraught with political risk and reward, say groups that track money in politics.

On one hand, Mills can use his own money to keep the race against Democratic Rep. Rick Nolan competitive in a sprawling swing district that spans two media markets.

Yet it's also led to accusations that Mills, whose personal fortune is linked to his family's chain of retail stores, is trying to buy the seat. The Mills Fleet Farm vice president is worth between $40 million and $150 million, according to personal financial disclosures.

"Mills' wealth itself isn't the issue," said Nolan campaign spokesman Kendal Killian. "It's the fact that he's using his inherited millions to get to Washington."

Mills is not alone in this regard. DFL Gov. Mark Dayton, an heir to the Dayton department store fortune, used some of his personal wealth to bankroll his gubernatorial bid in 2010. GOP gubernatorial hopeful Scott Honour, a wealthy investment banker, has already poured $900,000 of his own money into his first-ever run for political office.

As of late July, Mills had donated $167,000 to his campaign with the promise of more to come.

"He's not interested in running a campaign where he asks his supporters to do something he wouldn't also do himself," said campaign spokeswoman Chloe Rockow.

Nolan's campaign and Democrat-linked groups are making an issue of Mills' personal wealth and highlighting his opposition to a higher minimum wage.

The American Federation of State, County and Municipal Employees labor union and House Majority PAC, a Democrat-backed political action committee, rolled out a $150,000 ad buy against Mills, highlighting his "inherited millions" and salary that pays him more than a $500,000 per year.

"Attacking and demonizing a candidate's family for their success is a clear sign of desperation," said National Republican Congressional Committee spokesman Tyler Houlton.

Mills has outraised Nolan in three of the past four fundraising cycles and has a slight overall fundraising edge.

"This is not your normal self-funded candidate," said Michael Malbin, executive director of the Washington, D.C.-based Campaign Finance Institute. "He's demonstrating that he can raise money besides his own."

Expensive real estate

A seat in the U.S. House is expensive real estate, and subsidizing a campaign is no guarantee of success. Because of that, some wealthy candidates opt not to self-fund. Dayton spent a combined $15 million on his 2010 race and Senate race in 2000. This year he's vowed to spend no more than $20,000 on his re-election campaign.

In 2012, Democrat hotelier Jim Graves contributed more than $500,000 in a race that he lost to Sixth District Republican Rep. Michele Bachmann by less than 2 percentage points.

Republican U.S. Senate candidate Mike McFadden, an investment banker worth between $15 million and $57 million, has not contributed any of his own money to his campaign and has no plans to do so, aides said. McFadden is the leading Republican challenger to Democratic Sen. Al Franken.

"Every dollar we've raised and spent has been donated to this campaign, and that's how Mike plans to approach the rest of the race," said McFadden campaign spokesman Tom Erickson.

It cost $1.6 million on average to win a House campaign in 2012, according to a report by the Brookings Institution, a Washington, D.C.-based think tank.

Malbin expects outside cash to far outpace what the candidates in the Eighth District raise. In 2012, outside groups spent more than $10 million in the race.

Fight to the finish

Of the 23 self-funders who won races in the past decade, nine received at least half their money from other donors. Mills falls into that camp. So far, his campaign loan represents about 10 percent of the $1.13 million raised through the end of June.

Nationwide, loans that candidates make to their own campaigns represent 23 percent of the money raised by congressional challengers, said Malbin, of the Campaign Finance Institute.

Mills' fundraising prowess and willingness to tap his own financial well offers a clear contrast with Nolan, 70, who returned to Congress in 2012 after a 32-year hiatus. Nolan has resisted pressure from party leaders to spend several hours per day chasing campaign cash.

That refusal helped land Nolan in the Democratic Congressional Campaign Committee's Frontline program, which offers campaign and fundraising aid to the most vulnerable House Democrats. He's one of just 11 House incumbents who have been outraised by challengers this election cycle.

Nolan supporters note that he unseated the GOP's Chip Cravaack in 2012, despite Cravaack's $1 million fundraising advantage.