A key figure in the corruption scandals swirling around New Jersey’s disgraced governor is expected to plead guilty today in a case in which he is accused of hiring a prostitute to seduce government witnesses.

Wealthy real estate developer Charles Kushner, a fixture in New Jersey politics and society and a close associate of the resigning governor, James McGreevey, will likely serve months behind bars for his role in a lurid scheme against close relatives and a former accountant.

Mr. Kushner, 50, will appear before U.S. District Judge Jose Linares in Newark at 11 a.m., according to the judge’s staff. U.S. Attorney Christopher Christie is expected to hold a news conference following the court proceeding.

A spokesman for Mr. Christie, Greg Reinert, refused to comment. A lawyer for Mr. Kushner, Benjamin Brafman, did not return calls for comment.

Mr. Kushner is accused of recruiting a female prostitute to sleep with his brother-in-law, a witness in a federal investigation into whether Mr. Kushner violated campaign contribution laws through use of his real estate properties.

He is charged with obstruction of justice, conspiracy, and harming a witness. Under federal sentencing guidelines, pleading guilty to any of the counts leads to a minimum prison sentence of 15 to 21 months. That amount could be reduced with time off for good behavior.

A philanthropist, a major donor to a number of prominent Democrats, and a leading figure in New Jersey’s Jewish community, Mr. Kushner is chairman of Kushner Companies of Florham Park. He reportedly gave a total of $1.5 million to Mr. McGreevey’s political campaigns in 1997 and 2001. The governor also picked Mr. Kushner to be chairman of the Port Authority, but Mr. Kushner stepped down from the authority amid accusations of illegal campaign contributions.

He also sits on the board of trustees of New York University. A spokesman for the school, Josh Taylor, said NYU would “examine the issue” after a public announcement of the plea agreement.

The charges against Mr. Kushner emerged less than a month before Mr. McGreevey announced he was gay and had had an extramarital affair with a man, Golan Cipel, a former high-level aide to the governor and an employee of Mr. Kushner.

Mr. Cipel, an Israeli national, has denied the affair and has accused the governor of sexual harassment. His lawyers reportedly have accused the governor of offering hush money to Mr. Cipel, while the governor’s lawyers claim Mr. Cipel attempted to extort millions of dollars in exchange for silence.

No direct link has been found between the governor’s sex scandal and Mr. Kushner’s alleged plot against his brother-in-law, but some common threads have emerged, only adding to the intrigue.

For one, it was reported that Mr. Cipel’s lawyer agreed not to go public with the his client’s charges if the governor would assist in attaining a license for Touro College to establish a medical school in New Jersey.

Mr. Kushner is on the board of Touro College, a 34-year-old New York City based institution with a large Jewish student body. Touro College has denied any involvement in the alleged deal.

Mr. Kushner reportedly sponsored Mr. Cipel’s visa when the Israeli moved to America.

In 2003, the federal prosecutors in New Jersey launched a grand jury investigation into allegations Mr. Kushner violated federal tax and fraud statutes.

A federal complaint handed down last month by the attorney’s office alleges that Mr. Kushner orchestrated the video taping of a witness in the investigation – later identified to be his brother-in-law – in order to gain leverage over him. Mr. Kushner also sought to compromise another potential witness, his former accountant, who rejected the prostitute’s advances.

On December 4, 2003, the call girl met the brother-in-law at a diner near Bridgewater, N.J., and persuaded him to give her a ride to her hotel, claiming her car had broken down. She invited him to her room but he declined. The next day, he came back to her room and had sex with her.

One of the conspirators in the case videotaped the encounter and delivered the tape to Mr. Kushner, who later sent it to his sister, the wife of his brother-in-law. The brother-in-law has been reported to be William Schulder and his sister, Esther Schulder.

The criminal complaint said Mr. Kushner paid $7,000 to $10,000 to the prostitute and $15,000 to $18,000 to the two conspirators.