(CNN) - A former chief of staff to Rod Blagojevich pleaded guilty Wednesday to a single count of participating in a scheme to commit wire fraud related to the former Illinois governor's alleged efforts to profit off of his appointment of a replacement to fill the Senate seat vacated by Barack Obama.
Under the plea deal, federal prosecutors will ask that the defendant, John Harris, serve no more than 35 months in prison. Harris agreed to testify at Blagojevich's trial, set to begin June 3, 2010, said Randall Samborn, a spokesman for the U.S. Attorney.
"At times defendant assisted Blagojevich's efforts to carry out the scheme by suggesting means by which Blagojevich could secure personal benefits for himself in exchange for appointing a United States senator, conducting factual research relating to the scheme at Blagojevich's direction, and counseling Blagojevich on carrying out the scheme," the 25-page plea said.
"At other times, defendant expressed opposition to Blagojevich's efforts to enrich himself through his appointment of a United States senator, and/or did not follow instructions from Blagojevich to assist in those efforts," it added.
In January, the second-term Democratic governor was impeached and resigned. He has denied wrongdoing. He faces up to 20 years in prison for each of the 15 most serious charges in the indictment.
In April, a federal grand jury indicted Blagojevich on 16 felony counts.
Blagojevich has maintained his innocence throughout what has become a political soap opera.
Harris' plea agreement said the governor initially wanted to be appointed secretary of the Department of Health and Human Services and met last November with a Service Employees International Union official who he believed was working on behalf of President-elect Obama about filling the seat.
Blagojevich also expressed interest in an ambassadorship from Obama or a "high-paying position" with a private foundation in exchange for appointing "Senate Candidate B" to the seat, the agreement alleges.
When told that such a job might pay $200,000 to $300,000, Blagojevich appeared disappointed "and asked something like, 'Oh is that all?'" the agreement alleges. "At that point, defendant said that he thought the salary was more like $300,000 to $500,000. Blagojevich had a more positive reaction to that salary."
Blagojevich is also alleged to have explored the possibility of taking a job as national coordinator for an organization associated with labor unions called "Change to Win" in exchange for appointing "Senate Candidate B" to the vacant seat.
But soon after, "Senate Candidate B" got a job at the White House, after which Blagojevich allegedly told Harris to approach Senate Candidate D "to give Blagojevich some or all of Senate Candidate D's campaign funds" in exchange for the job, the agreement alleges.
Though he met with the candidate, Harris did not directly tell Senate Candidate D that Blagojevich was going to ask him for his campaign funds," it said.
For a time, Blagojevich is said to have considered appointing others, including himself, to the job. "For instance, with respect to appointing himself, Blavgovjevich expressed a variety of reasons for doing so, including to possibly avoid impeachment by the Illinois legislature, to obtain greater resources if he was indicted as a sitting senator as opposed to a sitting governor, and to facilitate his wife's employment as a lobbyist," it said.
After his wife got her securities license, Blagojevich asked Harris "to set up informational or networking meetings for his wife with financial institutions that had business with the State of Illinois in hopes that those businesses would assist in getting Blagojevich's wife a job," the agreement said.
When the governor decided that the institutions had been unhelpful in doing what he had sought, Blagojevich told Harris "that he did not want the institutions to receive further business from the State of Illinois," the agreement said.
Last November and December, responding to Chicago Tribune editorials critical of the governor, Blagojevich told Harris to tell a financial adviser to the newspaper that he was going to withhold state moneys from the newspaper "unless the Tribune owner fired people on the editorial board," the agreement said.
Though Harris met with the adviser, he did not pass along the threat, it said.
The governor ultimately appointed former state comptroller and attorney general Roland Burris - who was seated in the Senate despite protests from the chamber's Democratic leaders. Those leaders said a special election should have been called because of the controversy over the appointment.