Responding to one of the longest-awaited indictments in the annals of political skulduggery, Sen. Robert Menendez declared this week that federal prosecutors "don't know the difference between friendship and corruption." But the charges suggest it's Menendez who has trouble with that distinction.

The New Jersey Democrat's indictment on bribery and other counts depicts his relationship with a Florida eye surgeon, Salomon Melgen, as so mutually lucrative that it does not fit any commonly accepted definition of mere friendship.

The doctor's considerable qualities include the nation's most prolific Medicare billing and (despite his age and marital status) a stable of young, foreign girlfriends, according to the charges. But they do not include a New Jersey address. So Menendez's alleged advocacy for Melgen's $8.9 million in disputed federal fees and visas for his far-flung companions was for a man who isn't even one of the nine million people the senator is supposed to represent.

Perhaps Menendez was, as he contends, just helping a friend. That isn't the most scrupulous use of political power, but it is standard practice in New Jersey and, more important to the senator, a viable legal defense.

Or perhaps it's more believable that Menendez helped the doctor because the doctor helped him, to put it mildly. Melgen was responsible for more than $750,000 in political contributions to Menendez's 2012 campaign alone. He also treated the senator to numerous flights on his private jet, Caribbean vacations, and more. At one point, the indictment says, Menendez sent Melgen instructions to "call American Express Rewards" and book a $1,500-a-night Paris hotel room for him, the one with a "limestone bath and soaking tub with enclosed rain shower."

We could all use a shower after that. Thanks to Menendez's pugnacious personality and a high-powered legal defense that has already cost nearly $800,000, federal prosecutors face a fight to prove beyond a reasonable doubt that he committed a federal crime. But it's more than reasonable to doubt that the senator has given his constituents - the ones who live in New Jersey and don't tend to own airplanes - the representation they deserve.