President Obama no doubt hopes that Americans take at face value news that his justice department is preparing a criminal indictment for corruption of Senator Robert Menendez. The New Jersey Democrat is co-author of the bill designed to ensure that sanctions against Iran are brought back if the mullahs fail to reach an agreement or default on any agreement they do reach. It has driven Mr. Obama to a level of petulance America has rarely seen in a president. Yet voters are going to be asked to accept that the indictment is something other than retribution.

Good luck, we say. We don’t know Mr. Menendez, and he has a lot of doubters in New Jersey, which itself has a generally seamy reputation. The allegation seems to be that Mr. Menendez used his office help one of his friends, Salomon Melgen, a Florida ophthalmologist who is also a political donor to the senator. CNN, which broke the story of the pending indictment, notes that in 2013, Mr. Menendez described as an oversight his failure to properly disclose $58,000 in plane trips he took from Dr. Melgen as far back as 2010. The senator subsequently reimbursed for the trip and denies any wrongdoing.

We’re all for vigorous enforcement of the laws, and we’re for honest government (the newspaper whose flag we fly was famous for it). But the Justice Department’s record has been as disturbing as the crimes it has pursued. The most notorious case was its pursuit of Senator Stevens, the Alaska Republican who was indicted in 2008 and convicted and then lost his seat. Yet it turned out that the prosecution had been guilty of misconduct that a federal judge called “shocking and disturbing,” and Stevens’ conviction was vacated. It doesn’t take many moments like that to dilute the meaning of federal indictments.

In pursuit of Mr. Menendez the government has been trying to get past the speech and debate clause of the Constitution so as to read the senator’s email. The speech and debate clause says that for any — it uses the word “any” — speech or debate in either house a senator or representative shan’t be questioned in any other place. The clause is American bedrock, designed to protect the Congress from attack by the executive or judicial branch with which the Founders understood it would be in perpetual conflict of just the sort Mr. Menendez has found himself in with Mr. Obama.

A United States Appeals court has just overturned a district court that ordered Mr. Menendez to produce his email. The riders of the Third Circuit want a careful look at each email to see whether it relates to legislative business. Hmmm. The Constitution doesn’t protect speech and debate on only legislative matters; it protects, again, “any” speech or debate. No doubt there will be an effort to suggest it is improper of Mr. Menendez to use the speech or debate clause in this way. We see these constitutional protections as being there for a reason.

In any event, President Obama only a few weeks ago publicly accused his fellow Democrats of kowtowing to political donors over Iran. Mr. Menendez, according to the Times, stood up and told the president to his face that he took personal offense. Good for him. There is already some sentiment that Mr. Menendez should resign from the Senate; it will grow but stronger if an indictment is handed up. Better to let him stay in the Senate and hold a speedy trial, the right to which the Constitution also says he shall enjoy. We for one hope he turns out to be innocent and gets back to legislating a strong foreign policy.