The AP reports:
Federal authorities have opened a criminal investigation of Delaware Republican Christine O'Donnell to determine if the former Senate candidate broke the law by using campaign money to pay personal expenses, according to a person with knowledge of the investigation.
The person spoke to The Associated Press on condition of anonymity to protect the identity of a client who has been questioned as part of the probe. The case, which has been assigned to two federal prosecutors and two FBI agents in Delaware, has not been brought before a grand jury. [...]
At least two former campaign workers have alleged that she routinely used political contributions to pay her personal expenses in recent years as she ran for the Senate three consecutive times, starting in 2006. The Washington-based watchdog group Citizens for Responsibility and Ethics (CREW) filed a complaint with the Federal Election Commission making similar allegations and asked Delaware's federal prosecutor to investigate.
O'Donnell's campaign has denied wrongdoing, but acknowledged she had paid part of her rent at times with campaign money, arguing that her house doubled as a campaign headquarters.
Federal law prohibits candidates from spending campaign money for personal benefit. FEC rules say this prohibition applies to the use of campaign money for a candidate's mortgage or rent "even if part of the residence is being used by the campaign," although O'Donnell's campaign maintained that it was told otherwise by someone at the agency.
More at the link.