It was January 2018, and Senator Robert Menendez of New Jersey had just won a huge legal victory. His trial on federal bribery charges had ended in a hung jury, and the U.S. Justice Department had announced that it would not seek a new trial. He was free to walk with no criminal conviction, ready to take on another campaign for re-election.

Weeks later, he started dating Nadine Arslanian.

Ms. Arslanian, who would eventually marry Mr. Menendez, quickly introduced him to one of her longtime friends: Wael Hana, an Egyptian American businessman in New Jersey. The future Ms. Menendez was eager to connect her influential new boyfriend with Mr. Hana’s high-level connections in the Egyptian government.

What unfolded in the next four years is what prosecutors described on Friday as a sprawling corruption scheme that would ensnare the halal meat industry, American military aid to Egypt and the appointment of a top New Jersey law enforcement official. Prosecutors accused Mr. Menendez, 69, of abusing his power to influence arms sales to Egypt and to attempt to interfere with criminal investigations into Mr. Hana’s web of business associates.

An F.B.I. search last year of the couple’s New Jersey home revealed some of the fruits of their scheme, prosecutors said. Federal agents found more than $480,000 in cash stuffed throughout the house in envelopes and in the pockets of jackets that were embroidered with the senator’s name. Inside the home were more than $100,000 worth of gold bars, some of which had unique serial numbers that traced back to Mr. Hana. A shiny Mercedes-Benz convertible sat in the garage.

The 39-page indictment — which laid out in painstaking detail a series of deleted text messages, encrypted phone calls and shell company payments — painted a portrait of a couple motivated by relentless greed.

Ms. Menendez, 56, often pestered her associates for more bribe payments, prosecutors said, and did not hesitate to peacock her husband’s influence, once sending a news article to Mr. Hana about $2.5 billion of military sales to Egypt and writing, “Bob had to sign off on this.” The business associates around Mr. Hana seemed to find more and more ways to extract what they needed from Mr. Menendez, as long as they could deliver the cash.

The bribes even included two exercise machines and an air purifier that were delivered to the Menendez home, prosecutors said.

Mr. Menendez maintained his innocence on Friday, accusing the Manhattan federal prosecutors who brought the case of misrepresenting routine congressional work. Lawyers for Ms. Menendez and Mr. Hana, 40, also denied the charges.

When Ms. Menendez started dating Mr. Menendez in early 2018, she was unemployed. But her new relationship offered a solution.

Mr. Hana would agree to put Ms. Menendez on the payroll of his halal meat company if Mr. Menendez could promise to help facilitate more sales of military equipment to Egypt, prosecutors said.

At the time, the issue was a high priority for the Egyptian government because the U.S. State Department had been withholding some military aid until the country could show improvements on human rights. As the ranking member — and soon-to-be chairman — of the Senate Foreign Relations Committee, Mr. Menendez exerted significant influence over how much military aid the United States supplied to Egypt and other countries.

Mr. Menendez shared sensitive information from the State Department about the number and nationalities of people working at the U.S. embassy in Cairo with his girlfriend, who passed it to Mr. Hana, who forwarded it to an Egyptian government official, prosecutors said. Mr. Menendez also agreed to ghostwrite a letter from an Egyptian official who wished to urge the U.S. Senate for more military aid to Egypt.

In July 2018, after meetings between Mr. Menendez and Egyptian officials, he texted Ms. Menendez to tell Mr. Hana that he was going to sign off on a multimillion-dollar weapons sale to Egypt. Ms. Menendez forwarded the text to Mr. Hana, who sent it to two Egyptian officials, one of whom replied with a thumbs up emoji.

Mr. Hana and his business associate, Jose Uribe, then saw another opening to use Mr. Menendez, prosecutors said. They knew that Ms. Menendez had recently gotten into a car accident and needed a car, so they offered to buy the couple a new Mercedes-Benz C-300 convertible, worth more than $60,000.

In exchange, they asked Mr. Menendez to interfere in an ongoing prosecution and criminal investigation involving Mr. Uribe’s business associates. Mr. Uribe, 56, who worked in the trucking and insurance industries, had been previously convicted of fraud.

In early 2019, Mr. Menendez contacted a senior prosecutor at the New Jersey attorney general’s office who was supervising the cases and pressured him to resolve them favorably for the defendants, the indictment said. The prosecutor did not agree to intervene, but one of the cases ultimately resulted in a plea deal with no jail time. In the other, no charges were ever brought.

A few days after Mr. Menendez called the prosecutor, Ms. Menendez texted Mr. Hana: “All is GREAT! I’m so excited to get a car next week.”

She met Mr. Uribe in a parking lot of a restaurant, where he gave her about $15,000 in cash, and made the down payment on her new Mercedes the next day. “You are a miracle worker who makes dreams come true I will always remember that,” she texted Mr. Uribe.

But around this time, a problem arose. Mr. Hana’s halal meat company, IS EG Halal Certified Inc., had little to no revenue. Ms. Menendez, who prosecutors said had been given a “low-or-no-show job” there, started to complain to Mr. Hana’s business associates that she wasn’t getting paid. She texted Mr. Menendez about how upset she was about Mr. Hana’s broken promises.

A major break came in the spring of 2019. The Egyptian government gave Mr. Hana’s company a monopoly over certifying American food exports to Egypt as compliant with halal standards, in adherence with Islamic law. Mr. Hana’s company, despite its name, had no experience with halal certification.

A huge financial windfall was coming.

The day after an Egyptian official informed Mr. Hana that his company was most likely going to become the sole halal certifier for U.S. imports, Ms. Menendez texted the senator: “Seems like halal went through. It might be a fantastic 2019 all the way around.” The indictment did not say if Mr. Menendez used his position to influence Egypt’s decision.

Soon afterward, Ms. Menendez created a consulting company, Strategic International Business Consultants LLC, which prosecutors said was used to receive tens of thousands of dollars in bribe payments.

Mr. Hana’s monopoly, however, increased costs for some U.S. meat suppliers, which did not escape the notice of the U.S. Department of Agriculture. In the spring of 2019, U.S.D.A. officials asked Egypt to reconsider the monopoly rights for halal certification, which had previously been granted to a handful of companies.

At Mr. Hana’s request, Mr. Menendez called a high-level U.S.D.A. official and asked them to stop opposing the monopoly, prosecutors said. The official did not acquiesce to Mr. Menendez’s demands, but Mr. Hana still kept sole control over the Egyptian certification.

Two months later, prosecutors said, Mr. Hana used his halal company to pay about $23,000 to Ms. Menendez to help her stay current on her mortgage while she was in foreclosure proceedings.

Still, prosecutors suggested, Ms. Menendez felt she deserved more money for all the help that her boyfriend was giving Mr. Hana, especially after the senator had agreed to meet with some senior Egyptian officials. She texted Mr. Menendez: “I am soooooo upset.”

She wanted to complain to one of Mr. Hana’s business associates, but Mr. Menendez warned her: “No, you should not text or email.” She placed a call instead. The next day, Mr. Hana’s halal company wired $10,000 to her consulting firm.

As their scheme expanded, prosecutors said, they deleted more and more texts and emails.

A few months after the couple married in October 2020, Mr. Menendez met with Philip Sellinger, a potential candidate to be nominated for U.S. attorney in New Jersey, the top federal prosecutor in the state.

This time, the indictment said, Mr. Menendez was carrying out his end of another corrupt bargain. In the meeting, Mr. Menendez criticized the ongoing case against Fred Daibes, who was indicted in 2018 by federal prosecutors in New Jersey. He also happened to be a business associate of Mr. Hana and a longtime fund-raiser for Mr. Menendez.

When Mr. Sellinger said that he might have to recuse himself from the investigation anyway because of a prior conflict of interest, Mr. Menendez said he would not be recommending him for U.S. attorney, according to the indictment.

Ultimately, Mr. Menendez did recommend Mr. Sellinger for the nomination, believing that he could influence the investigation if Mr. Sellinger held that post, prosecutors said. The indictment did not say why Mr. Menendez believed that.

In early 2022, Mr. Menendez placed two phone calls to the federal prosecutor overseeing Mr. Daibes’s case. Minutes after the second call, Mr. Menendez called Mr. Daibes directly.

Two months later, Ms. Menendez ate lunch with Mr. Daibes and texted him afterward: “THANK YOU Fred,” with a slew of emojis. The next day, Ms. Menendez met with a jeweler who was friends with Mr. Daibes and sold the jeweler two gold bars that prosecutors believe were previously owned by Mr. Daibes, worth about $120,000 at the time.

The New Jersey U.S. attorney’s office did not bend to the pressure campaign, the indictment said. Mr. Daibes pleaded guilty in April 2022.

But the unraveling for the Menendez couple would soon begin.

In June 2022, federal agents raided their home. Some of the envelopes containing the wads of cash had the fingerprints and D.N.A. of Mr. Daibes and his driver — marked with Mr. Daibes’s return address, prosecutors said.

After the search, Mr. Uribe stopped making the monthly payments on the Mercedes convertible. Mr. Menendez wrote his wife a check for $23,000, part of which she gave to Mr. Uribe with the memo line: “personal loan.” The indictment did not make clear what the purpose of the payment was.

It was too late. On Friday, Mr. Menendez was indicted on three federal charges and temporarily stepped down from his chairmanship of the Senate Foreign Relations Committee. The indictment also charged his wife, Mr. Hana, Mr. Uribe and Mr. Daibes.

A lawyer for Mr. Daibes said he was confident his client would be exonerated of the charges. A lawyer for Mr. Uribe could not immediately be identified.

In response to growing calls for his resignation, Mr. Menendez issued a new statement late Friday.

“It is not lost on me how quickly some are rushing to judge a Latino and push him out of his seat,” he said. “I am not going anywhere.”

Tracey Tully contributed reporting.