Jose Uribe, the businessman who testified that he had bribed Senator Robert Menendez in return for his help in quashing criminal matters involving two of Mr. Uribe’s friends, was back on the witness stand Monday with a key question looming: Did he and the senator ever discuss the alleged deal?

Mr. Uribe has emerged as the prosecution’s chief witness in Mr. Menendez’s federal corruption trial, which enters its fifth week on Monday in Manhattan.

Mr. Menendez, 70, and his wife, Nadine Menendez, 57, have been charged with conspiring to take cash, gold, a luxury car and other bribes collectively worth hundreds of thousands of dollars in return for Mr. Menendez’s agreement to dispense political favors at home and abroad.

Mr. Uribe detailed one of those alleged favors in his testimony on Friday. He said he had been deeply concerned about an insurance fraud investigation by the New Jersey attorney general into two people close to him, and he raised the issue with a man named Wael Hana, a longtime friend of his and Ms. Menendez.

Mr. Hana told Mr. Uribe that in return for $200,000 to $250,000, he had “a way to make these things go away,” Mr. Uribe said.

“He could go to Nadine,” Mr. Uribe testified. “Nadine will go to Senator Menendez.”

Mr. Uribe testified that he later encountered the senator three times in person — at a fund-raiser Mr. Uribe said he organized for the senator to stay in his “good graces,” at a party held afterward and at a dinner. But Mr. Uribe said he did not broach the subject of the alleged deal with Mr. Menendez.