The change comes as CBS News and Sports President Sean McManus looks to boost the ratings of the third-place broadcast, which has attempted to offer viewers something a little different from the usual white-male talking head.
Under Ms. Couric, who is also managing editor, the show has been less formal and more likely to cover offbeat features than its rivals. (An early attempt at a nightly "Free Speech" segment, where famous and not-so-famous people were given a platform to air their views, has been cut back and will be used sparingly.) Despite the attempts to break the mold, "CBS Evening News" ratings have disappointed given the extensive promotion behind the arrival of Ms. Couric, who kicked off her $15 million contract on Sept. 5.
The executive change comes as NBC, the ratings leader, has faltered. ABC's "World News Tonight With Charles Gibson" took the lead for the February sweeps in the demo advertisers buy on-the 25-54 group-and also took the lead in total viewers. Still, no matter what changes Mr. Kaplan instills, there's no getting around an inherent challenge facing all of the evening newscasts.
"The bottom line is evening news is in a horrible time period," Brad Adgate, senior VP-research at Horizon Media, said. "Who is home at 6:30 p.m.? You can't expect softer news designed to attract younger viewers to get better ratings, because they are just not there to watch in the evenings. The right answer, and that's something they are doing, is to put the more homespun newscast online, which is where the younger viewers are."