A federal appeals court on Tuesday threw out the 4 1/2-year corruption sentence given to a long-powerful former Pennsylvania state senator, a victory for prosecutors who had sought at least 15 years for his crimes.

The court found that the trial judge abused his discretion in sentencing Vincent Fumo — without explanation — to a term far below federal sentencing guidelines. The court also upheld Fumo's conviction and ordered a new sentencing of an aide convicted at trial with him.

A jury in 2009 convicted Fumo of defrauding the state Senate, a museum and a South Philadelphia nonprofit of millions. The Philadelphia Democrat had been a wealthy power broker during his 30-year state Senate career. Prosecutors say he overpaid Senate and nonprofit staffers who then did his personal and political bidding around the clock.

They helped renovate his mansion, drove cars to vacation spots while he sailed on a borrowed museum yacht, spied on ex-lovers and political rivals, and, when the FBI came calling, helped erase email evidence on an array of computers and phones.

Fumo, 68, remains behind bars at a federal prison in Kentucky, with an expected release date of June 2013.

The 3rd U.S. Circuit Court found that Sr. U.S. District Judge Ronald Buckwalter brushed off more than $1.5 million in losses when he calculated the fraud at $2.3 million and erred when he said Fumo had not used "sophisticated means" or acted on behalf of a charity.

"This evidence of Fumo's intent to divert the funds (from the charity) was overwhelming, and the District Court's refusal to apply a two-level enhancement was an abuse of discretion," Circuit Judge Julio Fuentes of Newark, N.J., wrote in just one finding of error in the 62-page ruling.

Fumo's sentence created a firestorm in Philadelphia and Harrisburg, especially after Buckwalter praised Fumo for his "extraordinary" public service. By comparison, another federal judge called the conspiracy to destroy email evidence in the case "egregious" and sentenced the low-level Fumo aide to 2½ years.

The new fraud calculations could top $4 million and lift Fumo's guideline range to about 17 to 22 years, Assistant U.S. Attorney John Pease said Tuesday.

However, barring further appeals by Fumo, the case will go back to Buckwalter — who could reach the same 55-month sentence but simply explain his reasoning.

"There's nothing in the opinion that says the sentence has to be changed," defense lawyer Peter Goldberger told The Associated Press. "They did not find the sentence to be too lenient."

Fumo was convicted of all 137 fraud and obstruction counts after a five-month trial, and aide Ruth Arnao of all 45 counts. Prosecutors called the scope of Fumo's corruption "breathtaking."

Defense attorneys argued on appeal that Buckwalter was on solid legal ground in imposing the sentence. They said the fraud totals had been calculated fairly and the decision to credit Fumo for "good works" was deserved.

The appellate judges ordered Buckwalter to specify the departure awarded for good works, as higher courts have said such work is expected of public servants and not grounds for major departures.

Arnao, the only co-defendant to go to trial, received a one-year prison term, which will now also be revisited. Her husband, Fumo pal and former state Turnpike Commissioner Mitchell Rubin, served house arrest and agreed to repay $150,000 for a no-work senate contract awarded by Fumo.

Buckwalter set aside that loss at sentencing, saying he had not had time to weigh it. The 3rd Circuit ordered him to do so.

In a cross-appeal, Fumo had challenged the conviction on grounds of jury bias, citing a juror who hinted on Facebook that a verdict was near and another who said work colleagues had told her about a prior Fumo conviction. Fuentes called the online posts "harmless ramblings."

One member of the three-judge panel, Judge Richard L. Nygaard, supported the conviction but dissented on the need to resentence the pair.

"We are pleased with the decision of the 3rd Circuit Court of Appeals and will prepare for the next step in the process," said U.S. Attorney Zane Memeger.