Federal prosecutors are once again investigating U.S. Sen. Robert Menendez, according to a senior political advisor to the New Jersey Democrat, who has been the focus of two previous corruption probes — one that was later quietly dropped and a second that was dismissed after a high-profile criminal trial. “Senator Menendez is aware of an investigation that was reported on today, however he does not know the scope of the investigation,” said the advisor, Michael Soliman, who served Menendez’s state director and his New Jersey chief of staff. “As always, should any official inquiries be made, th…