U.S. Sen. Robert Menendez now begins a fight for his political life that could last for years. New Jersey would be better off if he would resign and conduct that battle on his own time.

The state needs a respected senator who is focused on his job, not a tarnished defendant who spends his days fending off credible charges of corruption and raising money for his legal defense.

Menendez vows that he will not resign. He argues that he should be regarded as innocent until he is proven guilty, a claim that cannot be taken lightly. But that is the standard for imposing criminal sanctions like jail and fines. For senators, the bar should be much higher.

Begin with this fact: Menendez admits that he took gifts from a wealthy Florida donor, Dr. Salomon Melgen, who twice flew the senator on a private jet to his home in a luxury resort in the Dominican Republic in 2010. Menendez also concedes that he kept those gifts secret, in violation of Senate ethics rules. He reimbursed Melgen only after he was caught.

That alone is a serious offense, and is not in dispute. It is at least as bad as the behavior that drove U.S. Rep. Rob Andrews (D-1st Dist.) from office in 2014 after he used campaign funds to finance trips to Scotland and Los Angeles. Andrews, who denies breaking ethics rules, at least had the decency to resign rather than put his constituents at a disadvantage while he fought for personal redemption.

The indictment charges that Menendez solicited gifts in return for specific officials actions. Menendez took private flights many more times than previously known, along with first-class commercial flights, a stay at a luxury hotel in Paris, and tens of thousands of dollars for his legal defense fund.

Menendez's supporters argue that prosecutors should not have the power to remove an office-holder chosen by voters. Again, that's a serious argument. But again it's unconvincing.

For one, voters would not have chosen Menendez if they knew this was in store. The Star-Ledger endorsed him for re-election in 2012, and like many voters, we have buyer's remorse. We did not have all the facts.

According to prosecutors, Menendez not only took these gifts, but returned the favor by using his office to benefit Melgen financially. He pressed Medicare regulators to change reimbursement policies in ways that would bring millions of dollars to Melgen, an eye surgeon. He asked the State Department to press the Dominican Republic over a port security deal Melgen had invested in, and he influenced the visa proceedings for Melgen's foreign girlfriends, according to prosecutors.

The challenge for prosecutors will be to prove the connection between Melgen's gifts and Menendez's favors. That would make his behavior criminal. That it was sleazy to accept these secret gifts in the first place is beyond dispute, even if the two are friends.

Yes, it is unnerving to effectively hand prosecutors the power to remove elected officials, especially when prosecutors have political ambitions themselves. And the Department of Justice in capable of making enormous mistakes, as when the second Bush administration famously botched the case against the late Sen. Ted Stevens of Alaska by withholding evidence from his defense attorneys.

But Attorney General Eric Holder has rebuilt the department's corruption unit, which has since scored several big wins, including the recent conviction of former Virginia Gov. Bob McDonnell. Menendez is among those who voted to confirm Holder, a show of confidence in his judgment.

The senator's legal team is trying to short-circuit this investigation by citing the Constitution's "speech or debate" clause, which prohibits the Department of Justice from interfering with lawmaking. That sounds desperate. Lawmaking is one thing; doing favors in return for big donations is something else.

Regardless of the outcome, it is hard to fathom Menendez's lack of judgment after a long career in a state that has been cursed by so much corruption. Why would he even dance close to this line?

He has done good service to this state over the past 40 years. But that is now tarnished forever. His decision to stay and fight only compounds the damage.

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