The well-respected former prosecutor is one of four prominent Arizonans who are now calling on the Justice Department to charge the Republican sheriff or else clear his name and put an end to the suspicion that has been hanging over his office for years. They wrote a letter last week to Attorney General Eric Holder, saying the nation's top lawman should decide immediately what to do.
"The only way to clear the air and resolve matters beyond a reasonable doubt is to meet before a judge and jury in a court of law," the letter said. "Or, if your investigation has not found sufficient evidence of wrong doing to bring criminal charges, you should say so now and end the investigation. Only definitive action by your Office one way or the other will end our long ordeal."
Arpaio, whose office did not respond to a request for comment on Thursday, has reportedly been under criminal investigation by the Justice Department since 2008. But the investigation has dragged on without anyone being charged.
Joining Charlton in writing the letter were three of Arizona's best-known politicians, two of whom are fellow ex-prosecutors: former Attorney General Terry Goddard (D), former Phoenix Mayor Phil Gordon (D) and former Maricopa County Attorney Richard Romley (R).
The four have been longtime critics of Arpaio, but they said the right thing for the Justice Department to do would be to clear the sheriff publicly if investigators have been unable to come up with enough evidence to charge him.
They also said they don't see how that would be possible. In their letter, dated last Friday and first reported by the Arizona Republic this week, the foursome pointed to a damning ruling by an Arizona Supreme Court disciplinary panel.
The ruling, which came down last week, said there was enough evidence to show "beyond a reasonable doubt" that Arpaio and three of his closest allies participated in a federal crime in December 2009.
The alleged crime didn't involve jail conditions, immigration enforcement or any of the things that made Arpaio notorious. Instead, it stemmed from a feud with other local government officials in Maricopa County.
Arpaio and his allies have been accused of using their law enforcement powers to target their political enemies, often investigating, arresting or charging them with crimes. The investigations rarely showed evidence of actual wrongdoing, and the disciplinary panel said the law enforcement actions were simply used as tools to humiliate political enemies.
In one example highlighted by the panel, Arpaio and his allies allegedly plotted to charge a judge with bogus crimes so that he would have to withdraw from a case in which he was expected to rule against them. The panel said that alone would be a crime and the evidence available would be more than enough to secure convictions of the people involved.
As a result, the disciplinary panel disbarred a pair of prosecutors that helped Arpaio in the crusade.
In the interview with TPM, Charlton called last week's ruling "extraordinary" and said it was what pushed the foursome to speak up.
"In my mind, that places the ball directly in the Department of Justice's court," he said.
Now in private practice in Phoenix, Charlton represented one of the targets of Arpaio's investigations, Maricopa County Supervisor Don Stapley. He also has plenty of experience with politically motivated scandals.
Appointed as the U.S. Attorney for Arizona under President George W. Bush, Charlton was one of eight federal prosecutors who were abruptly fired for what later turned out to be politically motivated reasons. The fallout from the firings eventually led to the resignation of U.S. Attorney General Alberto Gonzales.