“Gifts to cultivate friendship are not bribes,” Abbe Lowell said in his closing in defense of Democratic Sen. Bob Menendez — and enough jurors agreed to result in a hung jury and a mistrial.

The Biz Markie defense — he’s just a friend — worked. Lowell was worth every penny of the $4.5 million raised and spent by Menendez’s legal defense trust.

But the hung jury doesn’t change the facts:

Menendez’s co-defendant Salomon Melgen left the courtroom and went back to jail, where he is awaiting sentencing on 67 counts of Medicare fraud.

Menendez enjoyed ready access to Melgen’s private jets and luxury resorts financed by that Medicare fraud — and the New Jersey senator went all the way up the chain to the secretary of health and human services to keep the money flowing.

He got visas for Melgen’s supermodel girlfriends and he tried to steer a lucrative port security contract to the eye doctor who had no security background. Customs and Border Protection official Stephanie Talton testified that she found it “odd” that Menendez would “ask us to stop our law enforcement mission.”

Lavish gifts are sometimes used to cultivate friendships with sitting senators, it turns out, and once that friendship is cultivated, the senator is apt to do such friendly things.

It would appear that, after the Supreme Court’s decision in the Bob McDonnell case, that fact pattern does not establish bribery or honest-services fraud; absent a smoking-gun document or audio recording memorializing a specific quid pro quo, it’s hard to imagine what would.

The liberal ethics group CREW — with which I rarely agree — put it well: “Unless corruption laws are strengthened to fill the significant holes that the Supreme Court has created, the days of seeing corrupt politicians behind bars may be past.”

The jury could not reach a unanimous verdict even on Count 18 — making false statements — even though Evelyn Arroyo, the juror dismissed Friday, said in a Saturday interview that there was unanimous agreement Menendez was guilty on that count when the jury first voted. (She changed her mind the next day.) And even though the jury saw video of Menendez on CNN talking about his corrected disclosure documents and insisting he accepted only two flights — before a dozen more were discovered.

Maybe a new jury will see it differently if the Department of Justice retries the case next year.

But regardless of what happens in the criminal justice system, why did the Senate — which is supposed to enforce its own ethical standards — sit on its hands since many of the facts of the case became public five years ago? Why did they do nothing while Menendez delayed the start of his trial for years while he pursued the bizarre theory that the official acts he did for Melgen were constitutionally protected under the Speech or Debate Clause?

Senate Majority Leader Mitch McConnell responded to the mistrial by calling for Senate action.

“His trial shed light on serious accusations of violating the public’s trust as an elected official, as well as potential violations of the Senate’s Code of Conduct,” McConnell said. “Because of the seriousness of these charges, I am calling on the Senate Ethics Committee to immediately investigate Senator Menendez’s actions which led to his indictment.”

Better late than never.

Even if the criminal law has been so diminished that private jets and luxury resorts don’t constitute bribes, any reasonable standard of ethics tells us taking and concealing such gifts is wrong. Especially when they’re being given by a friend who runs a Medicare fraud scheme for which the senator actively lobbies.

A jury of Bob Menendez’s peers heard the evidence and the arguments, and some of the jurors agreed with the “just a friend” defense. Now the impetus is on the Senate Ethics Committee to do its job and, failing that, for the voters of New Jersey to conduct an act of political hygiene in next year’s Senate election.

Phil Kerpen is president of American Commitment.