For Robert Menendez, a senator set apart, closeness to rich donor draws scrutiny The intimate gathering stretched late into the night. Cigars and champagne toasts, a "picadera" of Dominican appetizers - only the finest at the well-appointed Caribbean retreat of the rich American doctor. Some of the moneyed attendees slipped into stylish guayaberas for the evening, but the guest of honor, Sen. Robert Menendez, stuck to a stodgy blue blazer with a pin on the lapel. The New Jersey Democrat posed stiffly beneath a huge cubist-style painting. He was the center of attention but still somehow out of place among the guests invited by his traveling buddy, the Palm Beach ophthalmology mogul Salomon Melgen. His friendship with Melgen, which has become the focus of a federal investigation, had brought him behind the gates of the ultra-exclusive Casa de Campo resort for an evening with heady company - Dominican elites, American entrepreneurs and international business executives. He was with them on that spring evening in 2010. But he wasn't really of them. Menendez, 59, had grown up without money and forged a career in the rough-edged landscape of New Jersey machine politics rather than the refined elegance of high society. He needed the rich as much - maybe more - than they needed him. "Bob is probably one of the poorest guys in the Senate," said Rep. Albio Sires (D-N.J.), his longtime friend and confidant. He has to scrap and scrape and claw and talk to people to try to raise that money. . . . It makes you vulnerable to something going on. Now Menendez's relationship with one of his wealthy patrons has drawn the scrutiny of the Senate Ethics Committee and a federal grand jury in Miami, which, according to three people familiar with the investigation, is examining his role in advocating for Melgen's business interests. Until Menendez's relations with Melgen drew the attention of investigators, the senator's influence in Washington had been growing. He had proved his bona fides as a fundraising powerhouse for Senate Democrats and a hero to Hispanic activists. He ascended last month to the coveted chairmanship of the Senate Foreign Relations Committee and emerged as a prominent player in one of the year's biggest legislative battles when he joined bipartisan talks over a possible landmark law to remake the U.S. immigration system. Melgen, toasting Menendez at the May 2010 reception at Casa de Campo, praised the senator as "not only the leader of Hispanic Americans in the United States but the leader of Hispanics in the Americas," according to a local society column reporting on the event. Melgen has been a prolific campaign donor, giving more than $700,000 to Menendez and other Senate Democrats ahead of last year's election. He has also provided the senator with free flights on his private jet and hospitality at his Dominican vacation home, according to people familiar with their relationship. Menendez has sought to apply pressure on the Dominican government to enforce a contract with Melgen's port security company and has interceded with federal health-care officials after they said Melgen had overbilled the federal Medicare program for treatment at his eye clinic.