NEW YORK — CBS News installed a new exec producer at the lagging “This Morning” on Wednesday, capping a series of other changes in the difficult ayem daypart.Al Berman, a former senior producer of “CBS Evening News” who most recently ran “Off Tenth” for the Eye on People cable web, will replace Jim Murphy as exec producer of “This Morning” and the early “CBS Morning News” that precedes it. Murphy will segue to senior broadcast producer, the No. 2 slot, at “48 Hours,” replacing Rand Morrison, who was named one of two senior producers at the new Bryant Gumbel newsmagazine. Morrison, as senior broadcast producer, and Nancy Duffy — who moves from the canceled “Coast to Coast” to become senior editorial producer — will be the key lieutenants for exec producer Michael Rubin at the still-untitled Gumbel show, which debuts Oct. 1. The series of changes comes nearly a year after an extensive reformatting at “This Morning” designed to increase the news hole filled by local affiliates and breathe some life into CBS’ dismal ratings in the daypart. The web is a distant third to NBC’s “Today” and ABC’s “Good Morning America,” whose own ratings woes led to co-anchor Joan Lunden’s replacement by Lisa McRee, announced Tuesday, and the naming of a new exec producer expected next week. But CBS hasn’t gained much momentum in the morning, where Murphy has produced the CBS shows since 1994. CBS News president Andrew Heyward denied that progress at “This Morning” was a factor in the producer shifts. While household ratings were up slightly in the May sweeps, to a 2.2 from a 2.0 last year, the standard 25-to-54 news demo is up 20%. “There is no sense in which Jim is being forced off the show,” Heyward said, claiming Murphy sought a change. “Three years is about the longest you can expect anybody to do that grueling shift.” Berman began his CBS career in 1986 as a producer at “CBS Morning News” and become senior broadcast producer at “CBS This Morning” a year later. He spent five years as senior producer at “CBS Evening News” before moving to Eye on People last year.