U.S. Sen. Robert Menendez noted last week that he and Dr. Salomon Melgen "celebrate holidays together, have been there for family weddings and funerals, and have given each other birthday, holiday, and wedding presents - just as friends do." The Florida eye doctor has also spent about a million dollars on campaign donations and vacations for the New Jersey Democrat, who brought Melgen's multimillion-dollar Medicare billing dispute to the attention of top government officials - just as friends, for the most part, don't.

A federal investigation of this apparently productive relationship is expected to yield charges soon, CNN reported last week. The headline led Menendez, the ranking Democrat on the Foreign Affairs Committee, to deny having done anything inappropriate and to remind the world of his close personal bond with the ophthalmologist in question. But the currency of this particular friendship hardly seems comparable to helping someone move a couch or springing for a round of beers - the sort of thing most of us expect from our friends.

As The Inquirer reported Saturday, Melgen has donated more than $900,000 to Menendez's campaigns and allied political committees. His private plane also collected the senator for vacations in the Dominican Republic twice in 2010. Amid scrutiny from the media, the Senate, and the FBI, Menendez paid Melgen $58,500 for the Caribbean vacations more than two years later.

As the nation's top recipient of Medicare payments, having collected more than $20 million from the program in 2012 alone, Melgen has not been without occasion to need a little help from his friend. With the federal government accusing the doctor of $8.9 million in overbilling, Menendez spoke personally on his behalf to the head of the Centers for Medicare and Medicaid services and then-U.S. Secretary of Health and Human Services Kathleen Sebelius, according to court records reviewed by the New Jersey Law Journal. Records and reports also indicate that Menendez and his aides repeatedly intervened to protect Melgen's contract to sell ship cargo screening equipment to the Dominican Republic.

An avid fund-raiser, Menendez has come under scrutiny for being a good friend to his donors before. Federal authorities' attachment to him dates to at least 2006, when he was first elected to the Senate amid an investigation of his rental income from a federally subsidized social services agency.

However, the veteran congressman's substantial record on foreign policy, immigration, health care, and more, along with his effective advocacy for New Jersey, helped him win a competitive 2006 race and an easy reelection in 2012, with The Inquirer's endorsement. He has recently been among the most prominent critics of President Obama's Iran policy.

Now the son of poor Cuban immigrants to hardscrabble Hudson County may be poised to join a veritable lineup of New Jersey senators tarnished by scandal, from Abscam target Harrison "Pete" Williams to another Bob who was friendly with a wealthy donor, Robert G. Torricelli. Menendez has vowed that unlike those predecessors, he's "not going anywhere." But if federal authorities find cause to charge him with a crime, he should take his next vacation from elected office.