The Correction Officers Benevolent Association last week mailed 50,000 palm cards to registered vo­ters in an effort to get them to raise questions about Mayor de Blasio’s proposal to cut the number of jail inmates in New York City to 5,000 and then close Rikers Island.

“Since Mayor de Blasio has refused to listen to our grave concerns about the 18-percent increase in jail violence, we’re taking our message directly to registered voters across the city,” said COBA President Elias Husa­mudeen. “We are not going to allow this administration to use their endorsement of the Lippman Commission’s report as a smokescreen to distract the public from the reality that the Mayor’s 14-point plan to end jail violence has failed.

“The public needs to ask Mayor de Blasio, as he visits their boroughs, what is his plan to deal with the most violent inmates who have been emboldened to continue their attacks on correction officers, civilians and inmates alike, as a result of his misguided policies.”

Mr. de Blasio last month reversed his opposition to City Council Speaker Melissa Mark-Viverito’s plan of closing Rikers. He said that a continually declining crime rate and the rise of programs to replace money bail with community supervision should make it possible to sharply reduce the average daily population from the current 9,300.

The city has about 2,400 beds in jails in Manhattan, Brooklyn, Queens and The Bronx. The Mayor said new jails would have to be constructed in each borough to provide an additional 2,600 beds. He said the City Council would have to take the lead in selecting sites, an assignment that Council Members have not embraced.

The correction unions have referred to Mr. de Blasio’s plan, and an accompanying report by a commission appointed by Ms. Mark-Viverito and chaired by retired State Chief Judge Jonathan Lippman that makes similar points, as “Fantasy Island.”

They said the Mayor had broached the plan in a year when he was seeking re-election to distract from what they call his failure to control rising violence on the troubled island.

The Mayor began a borough-by-borough “listening tour” last week in Staten Island. The palm cards were sent to 5,000 registered Republicans and 5,000 registered Democrats in each of the boroughs, the union said.

“No matter which side of the bars your family member is on, we all deserve to be safe,” the cards say. “Tell Mayor de Blasio that you demand safer conditions for everyone in New York City’s jails.”

By coincidence, less than 24 hours before COBA sent out its mailer April 13, the Mayor’s campaign committee emailed a letter in his name to people asking that they sign a petition supporting the plan to close Rikers.

In the letter, addressed to “Sisters and Brothers,” the Mayor stated, “The mass-incarceration crisis did not begin in New York City, but by making this important change, it will end here.”

The recipient of the letter who forwarded it to us had the cynical thought that there was an ulterior motive—a hope that those who agreed with his sentiments might also enclose a check to Mr. de Blasio’s campaign.