One way to make sense of the onslaught of political corruption investigations and prosecutions in recent years is to understand it as our legal system trying to draw the line between political misbehavior that is merely shady and that which is outright criminal.

Instead of looking at each of these cases in isolation, it makes more sense to see them as a pattern — and one that should provide some at least limited reassurance to President Trump, Prime Minister Netanyahu, and their supporters.

Begin with the Republican governor of Virginia, Robert McDonnell. He and his wife were indicted on federal corruption charges in 2014 and convicted by a jury on most counts that same year. In 2016, however, in the case of McDonnell v United States, the Supreme Court unanimously vacated the conviction, and the Justice Department subsequently dropped the case.

In 2015, federal prosecutors charged a Democratic U.S. Senator from New Jersey, Robert Menendez, in a similar corruption case. That case ended with a mistrial in 2017, and earlier this year, prosecutors announced they would drop the case.

The Democratic speaker of the New York State assembly, Sheldon Silver, was arrested in 2015 on similar corruption charges. A three-judge panel of the U.S. Court of Appeals for the Second Circuit last year overturned Silver’s conviction, and a retrial is scheduled for later this year.

The Republican majority leader of the New York State Senate, Dean Skelos, was also arrested in 2015 on federal corruption charges. His conviction, too, was thrown out by a federal appellate panel, and he, too, is set for another trial later this year.

That is four examples, featuring two Republican and two Democratic politicians whose prosecutions were originally brought in 2014 and 2015, when the White House and the Justice Department were under control of the Democrats. In all four cases, the prosecutors proclaimed they had caught a crime. In all four cases, judges or jurors disagreed.

In all four cases, the politicians, who pleaded not guilty, have suffered the punishment of public humiliation — negative headlines and unflattering photographs. Three of the four are no longer elected officials, though Menendez remains in office and is running for reelection this year. All four politicians have at least so far not had to serve the long prison terms with which they were threatened had they been convicted and had the convictions been sustained on appeal.

The McDonnell and Menendez legal cases are basically over, at least for McDonnell and Menendez. The Skelos and Silver stories, though, are still being written.

Even so, it’s not too early to draw the conclusion that prosecutors tend to overreach in these sorts of cases, imagining illegal corruption — bribery, conspiracy, obstruction, “honest services fraud” — where judges see routine constituent service. As Chief Justice Roberts warned in his opinion for the unanimous Supreme Court in McDonnell v. United States, under the sweeping interpretation of the prosecutors, “public officials could be subject to prosecution, without fair notice, for the most prosaic interactions.”

Prime Minister Netanyahu and President Trump, unlike Messrs. McDonnell, Menendez, Skelos, and Silver, have not been charged with any crimes. Mr. Netanyahu has a police investigation on his hands and Mr. Trump has a special counsel wanting to interview him after having filed charges against both his campaign manager and his national security adviser. In Mr. Netanyahu’s case, there is the added twist that the matter involves Israeli, not American law.

If the pattern holds, prosecutors will have a difficult time winning in court, and the cases will take a long time to work their way through the system. The political careers of those involved may nonetheless sustain damage.

Or maybe they won’t. Of all the precedents for political corruption, the most enduring and meaningful may be the case of James Michael Curley, who won election to Boston’s board of aldermen in 1904 while in prison for fraud.

It is a reminder that the really final and most important say in these sorts of cases belongs not to the prosecutors, nor even to judges and juries, but to the voters.