PHILADELPHIA — In what's fast becoming a family, political and legal drama in a Philadelphia courtroom, the estranged son-in-law of indicted state Sen. Vincent Fumo endured heated questioning Wednesday from Fumo's lawyer.

Fumo, 65, is charged in a 139-count federal indictment with defrauding the state Senate and others of more than $3.5 million, and then trying to systematically destroy e-mail evidence.

Son-in-law Christian Marrone, a key witness against the veteran Democrat powerbroker, testified Wednesday that he felt "betrayed" when he realized the extensive personal and campaign work he did for Fumo on Senate time was not proper.

The realization came after the ambitious, young Senate aide suggested that a Fumo-linked nonprofit — which the millionaire Fumo allegedly hit up for tools, vehicles and other assets — hire a better manager to counter press criticism.

"That would be nice, ... (but) if we had such a person and tried to do some of the things that are political, we would now have someone else 'in our tent' — and we would be subject to his blackmail if they so chose to do it," Fumo wrote in an e-mail reply shown to jurors.

Marrone has testified he spent much of his Senate time working on Fumo's mansion and helping with campaign or personal work. He admitted Wednesday that he and another senate aide took $8,000 from the South Philadelphia nonprofit, Citizens Alliance for Better Neighborhoods, to pay for a bar exam course.

Marrone also revealed that the rift between his longtime mentor came in part as he started to date Fumo's daughter Nicole more seriously, and saw how Fumo treated his eldest daughter. According to Marrone, Fumo had once written a letter to the private Baldwin School asking that Nicole be denied admission.