So who gives money to a mega-millionaire?

Suburbanites fed up with the city's leadership. Food-and-wine aficionados. Out-of-state businesses that wouldn't mind having a friend in City Hall.

And, of course, the millionaire himself.

On Sunday, Tom Knox, one of the five major Democrats in Tuesday's mayoral primary, pumped a fresh $1 million into his campaign as rival groups continued to attack him.

Including the $1 million he contributed the week before, Knox has poured in $9 million since he entered the race in late 2005, according to campaign-finance reports filed Friday.

All told, the former health-care executive and banker, who says he is worth $100 million, had raised just shy of $10 million, the rest coming mostly from people who previously worked with Knox, are enamored of his anticorruption message, or have a business interest in backing all five candidates.

Together, those donations account for about 9 percent of Knox's money, a higher percentage than the outside campaign funding collected by two other millionaires who financed their elections.

In 2005, New York Mayor Michael Bloomberg spent more than $70 million on his campaign, none from donors, and Gov. Corzine relied on donors for 5 percent of his contributions while he footed the bill for $43 million more, according to the nonpartisan Public Campaign Action Fund of Washington.

Money, of course, isn't everything. Knox's political fortunes have dropped a bit in recent weeks while Michael Nutter's have risen. Nutter, neck and neck with Knox in one recent poll, has drawn far more individual donors than Knox, illustrating a broad base of support. In the first four months of this year, for instance, Nutter counted seven donors for every one who gave to Knox.

An Inquirer analysis of Knox's contributions - absent his own - shows that just $1 of every $3 he raised came from residents and businesses in the city. Far more - almost half of his $850,000 in donations - came from Philadelphia's high-priced suburbs, including Bryn Mawr and Haddonfield.

Nearly $163,000 of the total rolled in from out of state.

"Tom is a pretty solid guy, and I think he would be a beneficial candidate for Philly, knowing the pains Philly is going through," said Thomas Scotto of Staten Island, N.Y. A third-party marketer of health-care plans, Scotto said he had met Knox through a mutual friend about two years ago. "I drove out to Philly. We sat down and had lunch. He was very courteous to me."

So when Knox asked Scotto to hold a fund-raiser in New York, Scotto complied.

"About 50 or 60 people showed up for the cocktail party," Scotto said. "People gave him checks for no more than $100 because, if I'm not mistaken, that's all he insisted upon."

Knox campaign spokesman Josh Morrow said that was "Tom to a T. . . . Tom is not someone who goes out and asks for a specific dollar amount. It's 'Whatever you can give me.' "

Knox collected far bigger checks from others in the health-care industry, including $20,000 from the Minnesota-based political action committee run by UnitedHealthcare, where Knox served as chief executive officer until he resigned last year to run for mayor.

He also received the maximum annual individual donation of $5,000 from several local health-care executives he has known or worked with, many with a long history of campaign giving in City Hall. They include Arnold Katz, president of Brokerage Concepts in King of Prussia, who gave $5,000 last year and $5,000 this year; Katz's wife, Bunnie, separately gave Knox $2,500 last year and $5,000 this year. Insurance executive William Graham IV, an investor in the company that owns the Inquirer, also donated $5,000.

Knox has attracted other traditional donors, as well, such as law firms that do business with the city.

"I understand the playing field is not level in terms of personal wealth of the candidates, but every candidate brings something different," said Mark Alderman, chairman of Wolf, Block, Schorr & Solis-Cohen in Center City. Through its political committee, the Ninth Decade Fund, the firm donated a total of $13,500 to Knox, and gave to his four rivals as well.

To be sure, some of Knox's donors said they had been moved solely by his message. In TV ads that have appeared for months, Knox has pledged to "take down the 'For sale' sign" at City Hall.

"I can't vote," said Anthony Jannetta, a 72-year-old registered Republican in Haverford, yet he gave Knox $200 in late March because "I think the city is overrun with bad management and corruption, and I think Tom brings a new, fresh face to it."

"I'm not totally convinced he can do the job," Jannetta added, "but he's smart enough to know where he's weak."

Philadelphia lawyer Norman Valz had never heard of Knox but contributed $500 after hearing him speak at a friend's house several months ago.

"I was very much impressed with the guy, that he was basically a self-made businessman and would bring business-oriented experience to the government of Philadelphia," Valz said.

Asked why he had given money even though Knox is wealthy enough not to need it, Valz said it was a way for him to "amplify" his vote.

Contact staff writer Marcia Gelbart at 215-854-2338 or mgelbart@phillynews.com.