[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2010/images/05/28/art.sestak.cinton.split.jpg caption="Former President Bill Clinton called Joe Sestak on the White House's behalf."](CNN) - Administration officials engaged in no improper conduct as part of alleged efforts to dissuade Pennsylvania Rep. Joe Sestak from launching a primary challenge against Sen. Arlen Specter, White House Legal Counsel Robert Bauer asserted Friday in publicly-released memorandum.
According to Bauer, Sestak was offered a high-level but unpaid position. Sestak turned the offer down, and ended up scoring an upset victory over Specter in last week's Pennsylvania primary. The White House was instrumental in last year's switch by Specter from the GOP to the Democratic party. It backed him in his bid for a sixth term in the Senate, and was eager to clear the field of any primary opponents.
"I'll have something for you later," Sestak told CNN Friday, as he walked to the House chamber for a vote.
A White House source also told CNN's John King, "Bill Clinton did talk to Sestak at the urging of Rahm, to discuss executive branch service based on the assumption he would stay in the House."
Thursday, in a press conference that largely focused on the BP oil spill in the Gulf Coast, President Barack Obama refuted allegations of impropriety surrounding reports that his administration offered Sestak a position if he would drop his Pennsylvania senate bid.
"I can assure the public that nothing improper took place," the President said toward the end of his hour-long news conference.
But Obama refused to give any more details, even as several Republicans and a handful of Democrats have demanded the White House be more forthcoming on the matter.
"There will be an official response shortly on the Sestak issue, which I hope will answer your questions," Obama said when asked about the issue. "You will get it from my administration. And it will be coming out, when I say shortly, I mean shortly. I don't mean weeks or months."
In February, Sestak, a former Navy admiral and two-term Philadelphia area congressman, said that someone in the White House last year offered him a job on the condition that he not mount a primary challenge to Specter.
Sestak had since refused to reveal any more details about the job offer – a pattern he continued earlier this week in an interview on CNN's "John King USA."
"I will let others speak for themselves," Sestak said when asked whom he talked to at the White House." I have said all I am going to say on the matter,"
But following the president's comments Thursday, Sestak said he would discuss the matter after the White House released its statement.
Since Sestak's May 18 primary victory, Republicans have been relentless keeping the controversy in the news. On Wednesday, all seven Republican members of the Senate Judiciary Committee called for a special prosecutor to look into the matter.
One of the unpaid positions that the White House suggested offering Sestak was an appointment to the President's Intelligence Advisory Board, which gives the president independent oversight and advice. But it was determined that Sestak could not serve on the board, since he was an active a member of Congress.
It appears that Emanuel picked Clinton as a go-between with Sestak because of the former president's stature as an elder statesman and prominent figure in the Democratic party, and because Sestak worked on the National Security Council during Clinton's years in the White House. Sestak backed former first lady and then Sen. Hillary Clinton in the 2008 Democratic presidential primaries.
Last week, before an appearance on CNN, cameras in the Russell Senate Office Building caught Sestak accepting a call from the former president.
According to a source at the State Department, Emanuel remains on a trip to Israel and is not expected back in the country until Monday.
–CNN's Dana Bash, John King and Deirdre Walsh contributed to this report.