"I know in my heart that I have not done anything illegal," the Philadelphia Democrat said during a 12-minute speech on the Senate floor, his voice at times somber, at times bitter.

"Sometimes in life the only choice we have when we face blatant injustice is to have the courage to stand up and fight. That is what I will do."

Fumo made the extraordinary remarks as lawyers close to the case said fraud, conspiracy, and obstruction-of-justice charges appeared imminent. An indictment could come as early as today.

Fumo stepped down from a powerful committee post yesterday - a day before the presentation of the annual state budget - but will remain in the Senate.

It was "a stunning development for the preeminent politico," said Fumo's longtime friend and fellow Democrat, House Majority Leader Bill DeWeese.

"There certainly has been only one Vince Fumo, and the long arm of the senator has exhibited unparalleled muscularity," he said.

After four years of near-silence on the investigation, Fumo, 63, a Philadelphia political baron and a Harrisburg fixture for three decades, said he expected the indictment to be voluminous - and misguided.

He predicted the indictment would focus on two basic allegations: that he exploited a South Philadelphia charity and misused his Senate staff for personal and political purposes.

It will not allege, Fumo said, that he ever cast a vote in his own interest or extorted money from businesses.

"The indictment will not allege that I ever accepted a bribe," Fumo said. "And, as the government knows, I never did."

Federal prosecutors John J. Pease and Robert A. Zauzmer declined to comment.

For nearly four years, the FBI and IRS have been investigating the finances of the multimillion-dollar charity Citizens' Alliance for Better Neighborhoods.

The organization, founded and run by Fumo allies, is funded mainly with public money and donations from Peco Energy Co. and the Delaware River Port Authority - money obtained through Fumo's influence or help.

The Inquirer has reported that the charity paid for political polls and secretly funded a lawsuit against a Fumo political rival. It is illegal for charities to participate in political activities and the IRS has been scrutinizing Citizens' Alliance tax returns to determine whether they were falsified.

Sources say the FBI is also investigating whether the charity bought Fumo household items and provided its SUVs - a Ford Expedition and a Lincoln Navigator - for Fumo to use on vacation.

Fumo defended his relationship with the charity.

"Make no mistake, I am proud of Citizens' Alliance," he said, ticking off a list of the nonprofit's accomplishments, from funding a charter school to cleaning up blighted neighborhoods.

The charity's lawyer, William J. Winning, declined last night to comment on the speech or the investigation.

In his speech, Fumo also defended his relationship with Harrisburg and Philadelphia staff. He said they work long hours serving constituents well.

"The suggestion that my staff members are political operatives or personal assistants reflects an amazing ignorance of both the legislative process and the facts," he said with a group of aides standing behind him on the Senate floor.

Fumo made no reference to possible obstruction-of-justice charges. Last year, two of his Senate computer technicians were accused of purging e-mails from government computers. In court papers, prosecutors said they believed the aides - Leonard Luchko and Mark Eister - deleted computer documents at Fumo's direction to thwart the federal probe. They have pleaded not guilty.

Several lawyers involved in the case said they expected the current charges against Luchko and Eister to be merged with the Fumo indictment.

Luchko's lawyer, James C. Schwartzman, said yesterday the government was overreaching.

"I'm looking forward to reading the novel the government is going to come out with," Schwartzman said. "If I were a betting man, I think we're looking at a couple of hundred pages."