Menendez is expected to appear in federal court in Newark Thursday in response to charges that he used the power of his Senate seat to benefit Dr. Salomon Melgen, a wealthy Florida eye doctor who prosecutors say provided the senator with luxury vacations, airline travel, golf trips and tens of thousands of dollars in contributions to a legal defense fund. The indictment, which marks the latest development in a federal investigation that came into public view when federal authorities raided Melgen's medical offices in 2013, will almost certainly lead to a drawn-out legal fight between Menendez and a team of Justice Department prosecutors who have spent years investigating his ties to Melgen. The criminal charges brought Wednesday cloud the political future of the top Democrat — and former chairman — of the Senate Foreign Relations Committee, who has played a leading role on Capitol Hill on matters involving Iran's nuclear program and U.S.