The Poulsens lent Bush their company jet during his campaign and gave more than $40,000 last year to the Florida Republican Party

Up to $2.5 billion in National Century money is unaccounted for, and an additional $400 million is missing from reserve funds used to back National Century bonds, according to company officials.

The Justice Department, the Securities and Exchange Commission and the Department of Health and Human Services, which investigates Medicare fraud, are looking into National Century's finances. Dozens of lawsuits around the country accuse Poulsen and National Century of defrauding investors and employees by skimming money from medical firms.

National Century, whose bonds carried Moody's highest credit rating less than two months ago, is operating under bankruptcy-court protection.

The company's rapid slide has revealed the financial strains in part of the nation's health care safety net. Unable to wait weeks or months for insurance companies to pay claims, 60 ailing companies relied on cash from National Century to run their medical offices and facilities. At least seven — serving thousands of mainly low-income patients from Los Angeles to Washington — have filed for bankruptcy protection since National Century crashed.

In Washington, Greater Southeast Community Hospital and Hadley Memorial Hospital — owned by Doctors Community Healthcare, a firm seeking bankruptcy protection — could not pay independent doctors on contract for several weeks. And Greater Southeast was forced to turn away emergency ambulances last month after the health care firms that provided contract nurses withdrew some nurses because of the cash squeeze.

Meanwhile, Poulsen and his wife, Barbara, have kept a low profile since mid-November, when FBI agents raided National Century's offices in Dublin, Ohio, and hauled away a truckload of computers and records. Poulsen's lawyer declined to make him available for an interview.

"Lance Poulsen is the most slippery character I've seen in my life," says Vicki Buba, an attorney at Stone Pregliasco Haynes Buba, which represents employees of a health care firm suing National Century in Louisville. "He and his people are getting away with murder."