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Maurice DuBois, a TV anchor who has won notice for his unruffled delivery of even the most shocking headlines, will leave CBS News amid a larger overhaul of the unit’s “CBS Evening News” after a revamp of its format spurred noticeable ratings declines.

DuBois revealed his departure Thursday via a post on Instagram, noting that December 18 would be his last day at the Paramount Skydance news division. He has spent 21 years at CBS-owned properties, primarily making a name for himself as an anchor at WCBS, the company’s New York flagship.

John Dickerson, the co-anchor of the current edition of “CBS Evening News,” announced his intention in October to leave CBS News His “Evening News.”

Such anchor departures, made without the naming of a replacement, are quite unorthodox, but CBS News is not operating in typical times. Paramount Skydance has set a non-traditional executive, opinion journalist Bari Weiss, as the unit’s editor in chief, and the exit of both men will give her a chance to put her stamp on the news division. And yet, Weiss has made outreach to several top TV journalists in recent weeks, according to people familiar with the matter, only to discovery that they are locked into contracts at other companies.

It’s no secret that “Evening News” has suffered in the ratings since executives at CBS News tried to focus less heavily on breaking headlines. Dickerson and DuBois made for an unorthodox pairing, with the latter offering smooth delivery and the former serving as more of a kinetic on-screen presence.

“CBS Evening News” won an average of nearly 4.26 million for the five-day period ending November 28, compared with 6.24 million for “NBC Nightly News” and 8.27 million for ABC’s “World News Tonight.” Among viewers between the ages of 25 and 54, the demographic most desired by advertisers,”Evening News” lured an average of 427,000, compared with 918,000 for “Nightly” and 1.03 million for “World.”

There are many who have wondered whether DuBois would be able to return to WCBS. His long run there and connection with viewers would be assets. And yet, Paramount has been whittling away at its employee base as it works to cut costs. Other top local anchors are departing, including Jim Donovan of Philadelphia’s KYW and Elliott Rodriguez at WFOR in Miami.