WASHINGTON — Federal authorities on Wednesday identified Democratic Representative Jesse Jackson Jr. of Illinois as the potential United States Senate candidate who was portrayed in court papers made public Tuesday as being the most deeply enmeshed in the alleged scheme by Gov. Rod Blagojevich to benefit from his appointment of a new senator to the seat vacated by President-elect Barack Obama.

A lawyer for Mr. Jackson acknowledged that Mr. Jackson was the person identified as "Candidate 5" in the criminal complaint, but said that Mr. Jackson denied any wrongdoing and was not aware of anyone cutting deals on his behalf.

“Congressman Jackson has never authorized anyone to seek the governor’s support in return of money, fundraising, or other things of value,” the lawyer, James D. Montgomery Sr., said at a news conference in Chicago. "Secondly, the congressman is not aware of any alleged associate having made such a proposal.”

A short time later, Mr. Jackson appeared at a news conference here in which he angrily denounced Mr. Blagojevich, called for the governor’s resignation and asserted that he had done nothing wrong.

“I never sent a message or an emissary to the governor to make offers plead my case or propose a deal about a United States Senate seat, period,” Mr. Jackson said. “I thought mistakenly that the governor was evaluating me and other Senate hopefuls based on our credentials and qualifications.”

“I did not know the process had been corrupted,” he added.

Mr. Jackson said that he would meet with federal authorities and cooperate “fully and completely” with the investigation. He did not take questions to address his role as the anonymous Candidate 5 identified in the affidavit against Mr. Blagojevich.

Mr. Jackson said in an earlier interview with ABC News that he did not know whether he was Candidate 5 but added that the prosecutors in Chicago told him earlier this week that he was not a target of the criminal inquiry. Mr. Jackson and his representatives campaigned for the appointment publicly and visibly throughout November, trying to make the case that he was the favored candidate. An official in Mr. Jackson’s office, Kenneth Edmonds, provided the New York Times with a poll that commissioned before Election Day showing Mr. Jackson to be the most popular choice among Illinois residents.

In the news conference, Mr. Jackson said he met with Mr. Blagojevich for 90 minutes on Monday to discuss the job after not having spoken with him for more than four years. Mr. Jackson, the son of the civil rights leader, said he never authorized anyone to offer anything in return for the appointment.

Earlier in the day, Mr. Jackson said in comments broadcast by ABC News: “It is impossible for someone on my behalf to have a conversation that would suggest any type of quid pro quo or any payments or offers. An impossibility to an absolute certainty.”

Federal prosecutors in Chicago would not discuss the identity of Candidate 5 and would not comment on whether Mr. Jackson would be interviewed in the case.

The identity of Candidate 5 has been a mystery since the filing of a legal complaint on Tuesday accusing Mr. Blagojevich and an aide of engaging in corruption and conspiracy, stemming in part from an alleged effort by the Governor to sell off Mr. Obama’s seat in return for campaign contributions and lucrative jobs for Mr. Blagojevich and his family.

Of the six candidates for the senate seat who are identified by number in the complaint, but not named, only Candidate 5 is said to have engaged in possible wrongdoing by engaging in discussions through an emissary about a possible quid pro quo with Mr. Blagovich’s camp. The emissary was also not identified by name.

According to the compliant, Mr. Blagojevich threatened to appoint Candidate 5 to the vacant post, rather than another candidate he thought Mr. Obama would prefer, if Mr. Obama would not help place Mr. Blagojevich’s wife “on paid corporate boards right now.”

The complaint also said that in a wiretapped conversation on Oct. 31, Mr. Blagojevich told an associate about an approach by the emissary from Candidate 5: “We were approached ‘pay to play.’ That you know, he’d raise me 500 grand. An emissary came. Then the other guy would raise a million, if I made him [Senate Candidate 5] a senator.”

Susan Saulny contributed reporting from Chicago.