Alexandra Wallace, a senior NBC News executive who has supervised everything from “Today” to “Meet the Press” and was regarded as the second-in-command at the sprawling NBCUniversal news division, is leaving the organization after a decade, a person familiar with the situation confirmed.

“Thank you @NBCNews for a great decade. Onward,” Wallace said on Twitter Friday. Her departure was reported previously by TVNewser.

Wallace leaves as NBC News is getting marching orders from a new guiding force. Andrew Lack, a former president and chief operating officer of NBC (in the days before it was transformed into NBCUniversal), was in April named to oversee both NBC News and MSNBC as both units faced difficult challenges. NBC News was in the midst of grappling with the fallout related to former “NBC Nightly News” anchor Brian Williams, and MSNBC has seen ratings slide precipitously over the last two years.

NBC News president Deborah Turness is expected to take over Wallace’s oversight of Washington, D.C., operations, the person familiar with the situation said. Janelle Rodriguez, who joined NBC News from CNN in late 2014 as a senior vice president of editorial, will get more oversight of “NBC Nightly News.”

Wallace had served as Turness’ deputy, and was charged with leading NBC News when Turness was away or otherwise occupied.

She has been NBC News’ go-to person to help smooth over trouble spots. In November 2012, she was placed in charge of all four hours of “Today” when that program was scrambling to reverse a decline in ratings in the aftermath of the dismissal of co-anchor Ann Curry. She was the first female executive to be given oversight of the franchise. In 2014 she moved to Washington to run “Meet the Press” after the program ran into headwinds while anchored by David Gregory, and continued to supervise it when Chuck Todd was named as its anchor.

Wallace got her start in the London bureau of CBS News and rose to become a senior producer for that network’s “The Early Show.” Along the way, she made stops at “CBS Evening News” and “48 Hours.” She joined NBC News in 2005 as an executive producer of “Weekend Today.”