CHICAGO, March 5 — In a cramped radio studio on a recent morning, a handful of candidates for the United States Senate were heaping scorn on an absent opponent — one with higher poll ratings than theirs, and a lot more money.

"We're on the poverty level compared to him," Maria Pappas, a Democrat, complained. Another Democratic hopeful, Joyce Washington, said solemnly, "If we start believing that a megamillionaire can come in here and buy a seat, this is a sad day."

The man they were grumbling about, Blair Hull, is undeniably rich. A former securities trader who began his climb to wealth counting blackjack cards in Las Vegas, Mr. Hull has promised to spend as much as $40 million of his own money in this campaign, more than any Senate candidate in Illinois has ever done.

But while Mr. Hull's lavish spending made him an early Democratic front-runner, his are not the only deep pockets in this race, one of the most closely watched in the nation. Seven of the 15 candidates hoping to succeed Peter Fitzgerald, a millionaire who is not seeking a second term, fall in the millionaire range themselves. Four are Republicans and three are Democrats, including the two women who complained indignantly about Mr. Hull — Ms. Pappas and Ms. Washington.

Americans have grown used to seeing rich political novices seek office, but rarely has one race drawn so many. They include a dairy owner whose name is ubiquitous on milk bottles, an investment banker turned schoolteacher, a paper company executive and a doctor turned high-tech entrepreneur. Of the 10 Senate candidates across the country who had given the most money to their own campaigns by the start of this year, 5 were running in Illinois, according to the Center for Responsive Politics.

"This is a race of the rich and of the really rich," said David Morrison, deputy director of the Illinois Campaign for Political Reform, a nonpartisan group. Six years ago, critics griped that Mr. Fitzgerald, a Republican and a relative unknown, was trying to buy the seat with $13 million of his own money. "Some of the rich people in this one," Mr. Morrison said, "would make Senator Fitzgerald look like a piker."

As the contests enter their final days before the March 16 primaries, nonmillionaire candidates are shaking commuters' hands at freezing El stops while rich ones continue their months-long barrage of glossy mailings and endlessly looping television advertisements. Some of the rich candidates are facing intense news media scrutiny for the first time, as embarrassing divorce records and awkward financial ties are exposed and pitilessly examined.

The wealthy candidates may all have been inspired by Mr. Fitzgerald's success in unseating Senator Carol Moseley Braun in 1998. Or the race may simply be, as some political experts here say, an extreme manifestation of a national phenomenon.

"This is a trend all through this business, of very wealthy people who want to get involved and leverage their wealth," said David Axelrod, a longtime political consultant from Chicago who is working for one of the nonmillionaires in this race: Barack Obama, a Democratic state senator.

Mr. Hull, whose net worth is $132 million to $444 million and who is thought to be the richest person ever to seek office in Illinois, is thoroughly unapologetic about his wealth, the soaring costs of his campaign, or his endless spots on TV. He boasts that he accepts no "special interest" money, no political action committee contributions — no contributions at all, in fact, over $100. Instead, he says, he has come up with his own peculiar mathematical equation — a mix of a voter's age, money, ethnic background and other identifying factors — to figure out which voters to woo with his own money. "We need to separate the money from the decision-making process, and I can do that," Mr. Hull said.

His poorer opponents, meanwhile, seem to point to their own lack of money as evidence of integrity and a common touch. Even the millionaires seem determined to distance their piles of money from Mr. Hull's.