The four-year investigation of State Sen. Vincent J. Fumo is coming to an end, and lawyers familiar with the case expect him to be indicted soon, possibly as early as Tuesday.

Fumo, one of the most powerful politicians in Pennsylvania, last year received a target letter - a formal notice that he is likely to face charges related to the fraud and obstruction-of-justice probe.

Fumo recently told people close to him to brace for an indictment, and has assured them that he will vigorously fight the charges.

"He's looking forward to clearing his name," said a person close to the Philadelphia Democrat. "He's kind of relieved the investigation is coming to a close."

Since 2003, the FBI and IRS have grilled everyone from Fumo's florist to a Senate-paid private eye. Agents have scrutinized Fumo's yacht trips, his finances, his use of legislative staff - and his aides' alleged cover-up.

But the heart of the case appears to be whether Fumo illegally exploited a multimillion-dollar South Philadelphia charity to fund his personal and political agenda - using it, as one person close to case put it, "as his personal piggy bank."

The charity, Citizens' Alliance for Better Neighborhoods, is funded mainly by public dollars and Peco Energy donations - most of the money won with Fumo's influence or help.

Early on, agents scrutinized those donations. Now, instead of pursuing how the money was raised, they are focused on how it was spent.

The Inquirer previously reported that the charity paid for political polls and secretly funded a lawsuit against a Fumo political rival.

The Inquirer has learned from sources that authorities are 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.

Last week in Harrisburg, Fumo walked away without answering when asked whether he expected to be charged.

Fumo, who has served in the state Senate for nearly three decades, has said the investigation is politically inspired by the Bush White House.

Now 63, he has long been respected and at times feared for his intelligence, political instincts, and network of appointees and allies.

Fumo has faced criminal charges before, only to prevail against them.

In 1973, five years before he became a senator, he was arrested on charges of vote fraud, but the charges were quickly withdrawn.

In 1980, a federal jury convicted him of putting "ghost" employees on the state payroll, but a judge threw out the conviction, a decision affirmed on appeal.

Citizens' Alliance was founded in 1991 by Fumo allies, including two legislative aides.

One was Ruth Arnao, a close friend and a senior staffer in Fumo's legislative office in South Philadelphia until 2004. Until recently, Arnao, 51, was executive director of Citizens' Alliance. She, too, received a target letter last year. Her lawyer did not return phone calls seeking comment Friday.

The senator has extolled the charity's good works: rehabbing the Passyunk Avenue commercial strip, subsidizing charter schools, and doling out grants to the likes of the St. Edmunds Golden Age Club, a legal clinic for the disabled, and the Anti-Defamation League.

FBI and IRS agents began investigating Fumo's relationship to Citizens' Alliance in 2004 after The Inquirer reported that the charity had collected millions of dollars in donations from unidentified sources.

The newspaper later revealed that the money had come from Peco Energy and the Delaware River Port Authority.

Peco secretly gave the charity $17 million as part of legal settlements in which Fumo agreed to drop his opposition to its business plans, the paper revealed. The senator has noted that Peco also agreed to cut bills to consumers as part of the settlements.

Fumo, long a power on the port authority, used his clout to obtain $10 million for Citizens' Alliance. The port authority is largely funded by tolls paid on its bridges and the PATCO commuter train.

Aside from the Peco and port authority money, Citizens' Alliance has received more than $4 million in state and other government grants.

As the federal probe nears its end, people knowledgeable about the inquiry say prosecutors have dropped the idea of bringing charges related to the Peco donations.

One source explained that prosecutors had concluded the donations weren't a crime because they had come as part of settlements in "real litigation," including a dispute over utility deregulation.

Fumo has portrayed his role in Citizens' Alliance as a patron.

"I don't get any benefits from it," Fumo said during a 2004 radio interview. "In fact, once in a while, I think they've picked up trash at my house and I've paid them $100 a month."

Trash pickup wasn't all that Citizens' Alliance did for Fumo, a source said.

On occasion, Fumo legislative aides drove Citizens' Alliance SUVs to Martha's Vineyard so Fumo could use them when he flew in for his annual vacations, according to a source familiar with the trips.

In a recent written response to Inquirer questions, Fumo's lawyer, Richard A. Sprague, said Fumo's work as a senator did not "cease even when he is on 'vacation.' "

Sprague said Fumo's Senate staff would drive office equipment to him - "computers, fax machines, etc."

"Sen. Fumo has long had the reputation as a tireless public servant whose efforts on behalf of Pennsylvania are not compressed into a 9-to-5, Monday through Friday schedule," Sprague wrote. "To the contrary, Sen. Fumo and his staff work 24/7 at the job of being the most effective Senate office in the commonwealth."

While Fumo has generally declined to talk about the investigation, his supporters have dismissed the inquiry as a witch-hunt that has ignored the good work of Citizens' Alliance and sought to criminalize mistakes and legitimate spending.

In reference to the lawsuit, the polls, and alleged obstruction of justice, Fumo's supporters offer explanations:

In 2001, the charity anonymously funded a legal challenge to then-Republican State Sen. Robert Jubelirer, a Fumo political enemy. The suit unsuccessfully sought to stop Jubelirer from serving simultaneously in the Senate and as lieutenant governor. Sprague has said the charity's payment was justified because the issue was of "great public importance." He suggested that the secrecy had been necessary to protect the nonprofit from "retaliation from the very officials involved in the litigation."

In 2002 and 2003, Citizens' Alliance paid more than $200,000 for political polling. After questions were raised, one of the senator's campaign funds reimbursed the charity. Fumo's supporters say it was an accounting error.

Last year, two former Senate aides, Leonard Luchko and Mark Eister, were charged with obstruction of justice, accused of deleting Fumo office e-mail as part of an effort to thwart the FBI investigation. In court filings, prosecutors have said they are investigating whether Fumo was involved in that alleged cover-up.

Fumo staffers have said that long before the investigation began, office policy required employees to delete old e-mail on a regular basis.

Prosecutors have tried to get Luchko and Eister to testify against Fumo - without success. Their lawyers say Luchko and Eister have done nothing wrong and have nothing bad to say about Fumo.

The grand jury investigating Fumo is set to expire within two weeks. Prosecutors have said they will complete their investigation by then.

Already, the grand jury has heard a mountain of evidence, generating thousands of pages of transcripts, a court filing shows.

FBI agents and prosecutors have issued scores of subpoenas. Seized e-mails alone run for 40,000 pages, prosecutors have said.

One other focus of the case has been Fumo's use of luxury yachts of the Independence Seaport Museum, where he sits on the board.

The museum leased one such boat for Fumo in 2001 at a cost of $13,375. He reimbursed the museum for the cruise in April 2004, three months after news of the investigation broke and more than 21/2 years after the trip, The Inquirer has learned.

Agents have conducted hundreds of interviews, seeking information from City Council members tied to Fumo, from the senator's political advisers - and from Frank Wallace, the private detective who has been retained by the state Senate Appropriations Committee.

Wallace's lawyer, Frank DeSimone, declined to comment Friday. It is not known why the FBI spoke with Wallace.

Two weeks ago, two of Fumo's close friends, South Philadelphia florists Jerry and Ann Catania, were seen trudging into the grand jury area. Their lawyer, Michael M. Mustokoff, declined to comment, and it could not be learned why the Catanias had been called to testify.

Fumo has long used the Catanias' business, Ten Pennies, to garland political fund-raisers. Since 2003, records show, Fumo's campaigns have paid the florists $176,000.

Contact staff writer John Shiffman at 215-854-2658 or at jshiffman@phillynews.com