WASHINGTON — Senator Clinton’s decision to return thousands of dollars from a top fund-raiser wanted as a fugitive in California illustrates the perils of the pellmell rush for political money — your friends can be your worst enemies. Just ask Mrs. Clinton and her rivals, Senator Obama and John Edwards. All three have experience putting out brushfires caused by former rainmakers.

Earlier this year, Mrs. Clinton divested her political action committee, Hill-Pac, of tainted contributions received from a Pakistani immigrant accused of plotting illegal donations. Mr. Obama donated to charity money he received in past campaigns from a Chicago developer caught in an Illinois corruption scandal. And just last week, the lawyer who represented assisted suicide advocate Jack Kevorkian was indicted on charges of conspiring to make more than $125,000 in illegal contributions to Mr. Edwards’s 2004 presidential campaign.

“We have a system where we try to make everyone a volunteer fund-raiser by setting targets and thresholds that can give an individual status as they are met,” said Anthony Corrado, an expert on political money at Colby College in Maine. Some fund-raisers may turn out to be “politically problematic.”

For Mrs. Clinton, this week’s news that one of her top fundraisers, Norman Hsu, had skipped his sentencing on a 1991 grand theft charge distracted her campaign just as it prepared to ramp up for the intense post-Labor Day stretch. The campaign announced Wednesday that it would return $23,000 in contributions that Mr. Hsu made to her presidential and senatorial campaigns and to Hill-Pac.