Charles Gibson retires at ABC; Diane Sawyer is new anchor

The generational shift in nightly news continues.

Charles Gibson is stepping down as anchor of World News Tonight at the end of the year, yielding his role on the second place network news broadcast to Diane Sawyer, his former Good Morning America co-host. Gibson has anchored World News since May 2006, when he took over shortly after Bob Woodruff, then the show's newly-appointed co-anchor, was badly injured by a roadside bomb in Iraq. Woodruff and Elizabeth Vargas had only just replaced Peter Jennings, who was forced to step down by the lung cancer that would kill him.