President Obama's chief of staff dispatched former President Bill Clinton last summer as an intermediary to see whether Rep. Joe Sestak would drop his planned run for the Senate if given an important but unpaid advisory position, the White House said Friday.

Clinton made the approach as Sestak was launching his challenge to Sen. Arlen Specter in the Pennsylvania Democratic primary, White House counsel Robert Bauer wrote in a report summarizing an internal investigation.

The counsel's office began looking into the matter in February after Sestak first stated that the administration had offered him a "high-ranking" job to stay out of the race.

The report disputed Republican contentions that conversations with Sestak about "options of service" on a presidential or other government advisory board were illegal or improper.

"There was no such impropriety," Bauer wrote. "The Democratic Party had a legitimate interest in averting a divisive primary fight and a similarly legitimate concern about the congressman vacating his seat in the House."

He said the suggestion originated with chief of staff Rahm Emanuel, who was eager to clear the primary field for Specter, who had just switched from the Republican Party and delivered crucial votes for Obama's agenda. But Sestak rejected the suggestion. Last week, he defeated Specter, and he now faces Republican Pat Toomey on Nov. 2.

In a statement Friday, Sestak confirmed the White House account. He said Clinton had called him last summer, "expressed concerns over my prospects" in the Senate primary, and then relayed Emanuel's suggestion that he serve on a "presidential board" while staying in the House.

"I told President Clinton that my only consideration in getting into the Senate race or not was whether it was the right thing to do for Pennsylvania working families and not any offer," Sestak's statement said. "The former president said he knew I'd say that, and the conversation moved on to other subjects."

Outside the Capitol later Friday, Sestak said he had spoken with Clinton about the matter for less than a minute. "There was nothing wrong that was done," Sestak said, according to the Associated Press.

Bauer's memo makes no mention of whether Obama had known about Clinton's role.

The controversy faded by the end of the Democratic primary, but it flared again after Sestak's victory, with Republicans renewing demands for an independent investigation into possible violations of the law.

Critics were not mollified by Friday's report. Rep. Darrell Issa of California, top Republican on the House Committee on Oversight and Government Reform, said he believed the offer was a quid pro quo.

"Regardless of what President Clinton or Congressman Sestak now say, it is abundantly clear that this kind of conduct is contrary to President Obama's pledge to change 'business as usual' and that his administration has engaged in the kind of political shenanigans he once campaigned to end," Issa said in a statement.

Republican lawmakers say a job offer could have violated at least two sections of federal law. The Hatch Act prohibits federal employees from interfering in elections or engaging in political activities, though elected officials and their senior advisers are granted some flexibility. Another statute makes it a misdemeanor to offer a job or anything of value in exchange for a political act or to support or oppose a candidate.

White House lawyers take the position that these statutes did not apply because Sestak was clearly qualified to be on an advisory panel and because it was unpaid. The legislative history of the laws suggests they were enacted to deter extortion.

Scott A. Coffina, a former associate counsel to President George W. Bush, said that the language of the Hatch Act and the criminal statute do not make exceptions for unpaid positions and that Emanuel seems to have been using his official authority to influence an election.

"This report doesn't make any of those questions go away or resolve the issue," said Coffina, a partner at Montgomery McCracken in Philadelphia.

The White House did not specify what options were presented to Sestak, though a source familiar with the situation said one idea that was considered, and then discarded, was a place on the President's Intelligence Advisory Board, which provides oversight on the nation's spy agencies. It was determined that Sestak could not serve on that board while remaining in the House, the source said.

Clinton seemed a logical choice to make the approach for the White House. He is a fan of Sestak, who worked in his administration as a top defense adviser. From 1994 to 1997, Sestak was a senior National Security Council aide, responsible for planning the administration's national-security strategy. Clinton also campaigned for Sestak during his first run for the House in 2006. Sestak was an early backer of then-Sen. Hillary Rodham Clinton in the 2008 presidential primary.

During the same time Sestak served on the National Security Council, Emanuel was a senior adviser to Clinton.

Issa and Republicans on the House Judiciary Committee wrote a letter Friday to FBI Director Robert Mueller asking for an investigation. The FBI, as is its routine practice, declined to confirm or deny whether it was or would be investigating.

During his campaign, Sestak rebuffed numerous questions about his dealings with the White House, saying only that he had been offered a job, but not what job or by whom. Sestak's long silence benefited his campaign, intentionally or not, analysts say, by feeding his "outsider" narrative with the image of a man standing up to power.

The White House also declined for three months to address Sestak's unusual claim, except for repeated assurances from press secretary Robert Gibbs that "nothing inappropriate" happened. But eventually the furor grew so intense that it put Obama - who has boasted of running the "most transparent" administration ever - on the spot, and it had to be addressed.

Toomey said in a statement Friday: "If this explanation is as innocent as it looks, I sure don't know why it took three months to say so. The White House and Congressman Sestak should have been forthcoming a lot sooner."

The Obama White House political shop - led by Emanuel, political director Patrick Gaspard, and deputy chief of staff Jim Messina - has a history of muscular but ultimately unsuccessful attempts to exert its will on campaigns.

In New York, Gaspard tried to push embattled Gov. David Paterson out of the 2010 governor's race. Paterson refused at first, but when a scandal overtook his administration, he announced he would not run.

And Messina suggested an administration job to Colorado House Speaker Andrew Romanoff in an unsuccessful bid to keep him from challenging Sen. Michael Bennet in the Aug. 10 Democratic primary, according to reports in the Denver Post.

Read the White House counsel's memorandum regarding Rep. Joe Sestak via http://go.philly.