Senator Robert Menendez of New Jersey faces new federal corruption charges, almost six years after a trial on unrelated claims of bribery ended with a hung jury.

Mr. Menendez, a Democrat who leads the Senate’s Foreign Relations Committee, has repeatedly said that he was willing to assist investigators and expected the inquiry would be “successfully closed.”

After a lengthy investigation led by federal prosecutors in Manhattan, a 39-page indictment unsealed Friday accused Mr. Menendez of sharing highly sensitive information about people assigned to the U.S. Embassy in Egypt and taking other steps that “secretly aided the Government of Egypt.”

It also names Nadine Menendez, his wife; Fred Daibes, a prominent builder who helped to rehabilitate New Jersey’s Hudson River waterfront; Wael Hana, the founder of a halal meat certification company with headquarters in New Jersey; and Jose Uribe, a former insurance agent from Union City, N.J.

Representatives for the senator, his wife and the three businessmen charged could not immediately be reached for comment.

Here is a closer look at the people at the center of the case.

Robert Menendez

Mr. Menendez, 69, is a political survivor. The son of Cuban immigrants, he rose to prominence in Union City, a small, densely populated community in Hudson County, N.J., a region known for its bare-knuckle politics.

He now lives in Bergen County with his wife of three years, Nadine Menendez.

They met years ago at one of his favorite haunts, an IHOP in Union City, a city he has represented as mayor and in the State Legislature and the House of Representatives before being elected to the Senate.

Mr. Menendez has been preparing to run for a fourth Senate term, and there are no indications that the indictment will change that plan.

He operates best under pressure, former aides have said.

He has had plenty of practice.

As a young man, he wore a bulletproof vest into federal court to testify against a onetime mentor, William V. Musto, then the mayor of Union City. Mr. Musto was convicted of taking hundreds of thousands of dollars in kickbacks from a contractor hired to build schools.

Soon after being sworn in to the Senate, he faced a federal inquiry led by Chris Christie, then the U.S. attorney for New Jersey, over payments by a nonprofit group that rented a house he owned. It went nowhere, but shadowed him for nearly six years.

In 2015, he stepped down as the lead Democrat on the Foreign Relations Committee after being charged with trading political favors for luxury vacations, golf outings, campaign donations and expensive flights. A nine-week trial in 2017 ended with a hung jury, and the Justice Department declined to retry him after a judge dismissed the most serious corruption charges.

Still, he was formally admonished by the Senate Ethics Committee, and had a closer-than-expected primary race with a largely unknown Democratic challenger. But he went on to beat his Republican opponent handily in November 2018.

Nadine Menendez

Ms. Menendez, 56, got engaged to the senator in October 2019 after a whirlwind courtship; they married a year later in a small ceremony in Queens.

Ms. Menendez, who speaks several languages and has a master’s degree in French from New York University, started an international consulting company in June 2019.

A law firm run by a longtime friend of Mr. Menendez filed the incorporation papers for the company, Strategic International Business Consultants, on the same day that a lender began foreclosure proceedings on the split-level home in Englewood Cliffs, N.J., where she and Mr. Menendez now live, according to state records and court filings.

By the next year, her finances had rebounded.

Mr. Menendez reported on Senate disclosure forms that in 2020 his wife owned bars of gold bullion worth as much as $250,000. Federal records show that the couple recently sold the bullion for as much as $400,000, a sum that would be the equivalent of roughly 14 pounds of gold.

Fred Daibes

Mr. Daibes, a prominent real estate developer based in Edgewater, N.J., lived in a Palestinian refugee camp for 10 years before emigrating to the United States as a child. He worked his way up from washing dishes in a New Jersey restaurant to acquiring wealth so vast that in 2013 several people were charged with beating him and stealing millions of dollars worth of gold and jewelry from his penthouse apartment, court records show.

Five years later, Mr. Daibes was charged with a bank fraud scheme in a 14-count federal indictment.

Last year, he pleaded guilty to a single count of making false entries in connection with a loan document. Prosecutors said it was part of a scheme by which he obtained the proceeds of an insider loan from Mariner’s Bank, which he founded and where he had served as chairman. The $1.8 million loan was paid back, and the plea agreement, approved by prosecutors in the U.S. attorney’s office in New Jersey, did not call for prison time.

Mr. Daibes’s sentencing has been delayed four times, most recently in July.

While awaiting sentencing, the judge granted Mr. Daibes permission to travel to London and Qatar to meet with potential lenders for a real estate project at 115 River Road in Edgewater, N.J., which had lost its financing after getting bogged down in a delayed environmental cleanup, court records show.

The trips paid off.

In January, he finalized a $45 million shared-ownership agreement for the Edgewater project with a company founded by a member of Qatar’s royal family, Bergen County deed records show.

Wael Hana

Wael Hana, 40, has known Ms. Menendez since before she began dating the senator. They socialized together at restaurants in Bergen County, N.J., with a small circle of friends, according to members of the group.

In the spring of 2019, Mr. Hana, a U.S. citizen born in Egypt, began operating a halal meat certification company in New Jersey, even though he said in court documents that he had no experience in the industry.

By January 2020, the company, IS EG Halal, was the sole entity authorized by the Egyptian government to certify that any halal food product imported into Egypt from anywhere in the world had been prepared according to Islamic law.

The arrangement did not require the approval of the United States, according to the Department of Agriculture. But it meant that four U.S.-based halal meat certification companies that for years had shared the work lost the business overnight.

In November 2019, federal agents searched Mr. Hana’s home and office, seizing computers, cellphones, paperwork and jewelry, according to legal papers his lawyer, Lawrence S. Lustberg, filed to retrieve the items.

IS EG Halal operates from a small building overlooking the Hudson River in Edgewater, in a building owned by a company run by Mr. Daibes. Mr. Daibes also has an office in the building.

A spokeswoman for Mr. Hana has said that he won the halal certification contract without any help from Mr. Menendez or any other U.S. official.

Kirsten Noyes contributed research.