Clinton Campaign Cites Flawed Background Check

But several former regional fundraising advisers to the Clintons said in interviews yesterday that they could not recall whom, if anyone, had vouched for Hsu when he started raising money for the senator.

McAuliffe, the man who built his reputation by raising huge sums for Bill Clinton, said it was not until 15 months after Hsu wrote his first check to Clinton's Senate bid that they met, "and I had very little interaction with him after."

Major Clinton donors said this represents a departure for a campaign that prides itself on preparation and will not hesitate to lavish attention on those who raise money.

Irvine, Calif., businessman Jack Cassidy told the FBI that he sent at least three e-mails to a Clinton campaign official on the West Coast this summer, specifically raising concerns that Hsu was engaged in a risky investment scheme and was using Hillary Clinton's name "in vain" to solicit people for his business proposition, according to a person directly familiar with the matter.

Cassidy's concern was that Hsu was using the Clintons to give credence to his business venture, the source said, speaking only on the condition of anonymity because of the ongoing FBI inquiry.

Cassidy also raised his concerns with local police, the local prosecutor, California Democratic Party officials and the FBI, which dispatched agents to interview him and collect documents in recent weeks about Hsu's business and fundraising activities.

Clinton spokesman Wolfson said the campaign did an initial public records search in January when Hsu began raising money. The inquiries from Cassidy this summer prompted the campaign to do a second vetting of Hsu, which turned up nothing derogatory. "When the concerns were raised, we again checked publicly available information and unfortunately did not find this decade-plus old warrant," he said.

Research editor Alice Crites contributed to this report.