The Washington Post is reporting that New Jersey Democratic Senator Robert Menendez is being investigated by a Miami federal grand jury for his role in advocating for the business interests of a wealthy donor and friend.  A story on the newspaper's website says that as part of the probe federal agents have questioned witnesses about the interactions between Menendez and Florida ophthalmologist Salomon Melgen. The newspaper cites unidentified people it says are familiar with the proble. Menendez has raised questions with U.S. officials about the Dominican Republic government's failure to honor a port security contract involving Melgen, and he contacted U.S. health agencies to question their billing practices and policies amid a dispute between Melgen and federal authorities. The Post says Melgen declined to say yesterday whether he knew anything about the investigation, but he says any probe will find no wrongdoing.